Rome Always Raised Another Army

Asked for the big difference between the ancient world and now, Gregory Aldrete does not start with technology, though the gap is obvious. The more interesting differences, he tells Lex Fridman, are structural. Until the Industrial Revolution, Greeks, Romans, Egyptians, and everyone else buried about 30 to 40 percent of their children before puberty. An ordinary ancient person would have lost three or four kids, watched siblings die, and, if a woman lived to about thirteen, given birth four or five times just to keep the population from shrinking. That mortality, he says, is a huge psychological divide.

Human nature, in the crude sense, he thinks is roughly constant: fear, greed, love, and the forces that produce war keep showing up. What he likes as a historian are not the polished literary sources but tombstones, graffiti, and scraps of parchment that record a sale. Those fragments give him a spark of sympathy across two thousand years, and also the opposite jolt, when an ancient act is simply incomprehensible. Understanding a foreign culture, he argues, begins when you line those two feelings up.

The other forgotten fact is that almost everyone was a small family farmer. If a textbook of the Roman Empire were honest, Aldrete says, nine of ten chapters would describe that life: a village you never left by twenty miles, marriage to someone from there, decades in the dirt, then death, without a battle, a statue, or a philosopher. Emperors and artists still carve history, and there is a reason we focus on them. He just does not want the 80 or 90 percent who never appear in the story written out of it.

Rome's other strangeness is its obsession with the past. A Roman aristocrat walked into a cabinet of wax death masks and had memorized every office and battle those faces had held. Kids wore the masks in funerals. Five hundred years after Lucius Junius Brutus helped expel the kings, Julius Caesar started acting like one, and graffiti on Marcus Junius Brutus's house told him to remember his ancestor. He joined the Ides of March. Aldrete asks his students how many would knife their best friend because of a great-grandfather many times removed. For Brutus, there was no choice. Tradition, the *mos maiorum*, gave Rome strength and locked it against the changes that might have saved the Republic.

Roman history, Aldrete says, comes in three governments. From roughly 750 to 509 BC it was a monarchy of undistinguished mud huts. A revolution made a republic that lasted about five hundred years: first the conquest of Italy, then the Mediterranean. Then came emperors, starting with Octavian, later Augustus, a one-man rule the Romans insisted was not kingship. The conventional end is sometime in the fifth century AD, another tidy five hundred years, though Aldrete is willing to run the Eastern empire to 1453. Western later ages picked the piece they wanted: revolutionary America and France gazed at the Republic, while Mussolini, Hitler, Napoleon, and Victorian Britain gazed at the Empire.

Classical Greece peaked earlier, then fell under Rome in the Republic's second half. Romans treated Greek culture as one more arena of aristocratic competition, learning Homer to out-quote one another. Before the Greeks came the Etruscans of northern Italy, who gave Rome, or from whom Rome took, the toga, gladiatorial games, and much of its religion, from Jupiter as a thunder god to reading livers and bird flight. Lex calls it stealing with a bad name; Aldrete agrees that the talent for absorbing other people's best ideas is one of Rome's secrets, not every empire's.

The military secret of early Rome was not better generals, weapons, or tactics. It was manpower. The ancient default after taking a city was to kill most of the men and enslave the rest. Rome sometimes did that too, but with fellow Italians it more often left them in place, shared full or half citizenship or an alliance, and, instead of heavy taxes, always demanded troops. Those soldiers became a machine of Romanization. When the Greek colony at the toe of Italy hired Pyrrhus of Epirus, a man who thought himself a new Alexander, he wrecked two Roman armies and waited for a treaty that never came. A third army appeared. He could not replace his dead; Rome could. An officer said fighting Romans was like fighting a hydra. Pyrrhus went home having won the battles and lost the war.

Under the emperors the same habit scaled up. Conquered chiefs' sons were raised at Rome. Auxiliaries, about 250,000 of them beside 250,000 citizen legionaries, served twenty-five years and left as citizens whose children became legionaries. By the second century AD, Trajan and Hadrian were from Spain; a century later Septimius Severus was from North Africa, with later emperors from Syria. The leaders of the empire were coming from the provinces. That openness, Aldrete argues, is why a village of huts became the Western paradigm of a successful empire.

Once Italy was in hand, Rome stepped into a different world: people who did not share its gods, language, or economy. Its rival in the west was Carthage, founded at about the same time, a merchant oligarchy with a small citizen body, maritime trade, and hired armies, set against Rome's citizen-soldier farmers. Geography made the collision feel inevitable. Sicily sat between them, then Spain, then a town called Saguntum on the border of Spain and Gaul. The three Punic Wars were, in Aldrete's telling, a map reading itself aloud.

The Second Punic War matters because Carthage produced Hannibal Barca, a military genius and son of the general who had fought Rome for Sicily. Hannibal saw that Rome's strength was the Italian allies. He would not wait in Spain or Africa. He crossed the Alps with elephants, an act nobody thought possible, and massacred the first army sent against him, then the second. Rome spent two years raising two armies at once. That was Cannae. Facing about 80,000 Romans, Hannibal used double envelopment: weaker troops in the center holding or giving ground, better troops and cavalry crushing the wings and closing from behind. In one afternoon he killed about 60,000 Romans, more men hacked to death with swords than Americans who died in twenty years in Vietnam, and far more than the roughly 15,000 dead at Gettysburg over three days.

It was the closest the Republic came to death, the furnace, Aldrete says, between one more rising power and the dominant state in the Mediterranean. Rome's response was to stop fighting him. Armies followed Hannibal around Italy and backed off whenever he turned. Meanwhile they attacked other Carthaginians in Spain. Necessity produced Scipio, who took Spain, crossed into North Africa, and threatened Carthage itself. After more than a decade marching undefeated in Italy, Hannibal was called home. At Zama his men were old and Scipio had the advantages. Carthage lost. From the war's end in 201 BC, Rome was the first power of the Mediterranean, and it turned east toward the richer Greek world left by Alexander's generals.

The double envelopment became a template. Aldrete points to German cauldron battles on the Eastern Front and even the Gulf War's envelopment of Iraq. Hannibal's other gifts were troop types and terrain: the misty ambush along Lake Trasimene, when a Roman army was strung out in marching order, is the other famous example. The Greek historian Polybius, whose city Rome captured, wrote his history to explain how Romans could conquer the entire Greek world in fifty-three years. To the Greeks, the Romans were uncouth barbarians. The army that had survived Hannibal did not look uncouth for long.

From the Greeks through the Romans, the Mediterranean's military thread is heavy infantry. Greek hoplites wore heavy armor, carried a spear and a huge shield, and shuffled forward as a bristling mass that was nearly invincible head-on and dead from the side or rear. Alexander lengthened the spear into the roughly fifteen-foot sarissa, so long that shields barely mattered, and used that frontal shock to take the Persian Empire. The Romans kept heavy infantry but fought up close with short swords, and they cut the army into nested units: eight men in a tent group, ten of those in a century, then cohorts, then a legion. Flexibility was the point.

In 197 BC at Cynoscephalae, a Roman legion met a Macedonian phalanx still running Alexander's system. Head-on, the sarissas were going to win. The Romans peeled off a section, ran to the flank, and ended the battle. Military history, Aldrete says, is development and counter-development. You have to keep adapting. The classic imperial legionary of the first and second centuries AD wore the *lorica segmentata*, steel bands like a lobster shell, a helmet, a curved square shield, and the *gladius*. Every piece was still handmade. There were no factories stamping out ten thousand identical kits.

Aldrete's own accident in armor began with an undergraduate, Scott Bartell, who had *Alexandros* tattooed in Greek on his arm and had built himself a copy of the linen cuirass Alexander wears in the Pompeii mosaic. No examples survive, because organic armor rots, and scholarly articles on the linothorax barely existed. What followed was a ten-year project with about 150 students, other faculty, three documentaries, and a scholarly book. They found 65 literary mentions by 40 authors and about a thousand images in art, reverse-engineered a pattern, grew flax, spun thread, used rabbit glue, and shot the result with reconstruction arrows and bronze heads from ancient battlefields. A one-centimeter linothorax protected about as well as two millimeters of bronze, the thickest comparable plate of the time, at about eleven pounds against some twenty-four to twenty-six for bronze and twenty-seven or twenty-eight for mail.

Lighter armor meant more endurance in Mediterranean heat, and any woman who already spun and wove could have made one at home. Ancient glues were probably better than theirs: metal on a helmet fished from a German river was still stuck after two thousand years underwater. They chose a least-common-denominator recipe so the reconstruction was something they knew ancients could have made. By Roman times the linothorax left the front line, as steel-like edges and composite bows made fabric easier to cut. It survived as hunting kit against big cats and as a stab-proof layer under a toga.

Alexander, Aldrete says, had the full kit: intelligence, athleticism, charisma that filled a room, and luck. The luck was Philip II, who reformed the Macedonian army, issued the sarissa, and built a mixed force of heavy and light horse, heavy and light infantry, and missile troops. Alexander used that tool with a flexibility most earlier battles, two lines smashing together, never had. He also pushed a cultural program that still splits readers. A Macedonian who adopted Greek culture, he later wore Persian clothes, married a Persian wife, forced thousands of his men into local marriages, appointed Persians, and folded Persian units into the army. His old guard wanted the old model: we conquer you, you are slaves. Every generation, Aldrete notes, remakes Alexander as Aristotelian visionary, egomaniacal war-monger, or alcoholic. The real motives are a mixed message.

Why Rome lasted and Alexander's empire did not is, for Aldrete, a clear answer. The moment Alexander died, the thing came apart. It had been personal loyalty and charm, with no structure and no succession, a spectacular ten-year flash. The Romans were imperialist and capable of wiping out cities, and Aldrete will not whitewash them. On the whole they were much more about bringing people into the Roman project. That, not a single genius, is why their system could rejuvenate itself.

If one Roman legacy still sits under daily life, it is law. Aldrete estimates that something like 90 percent of the world uses a system directly or indirectly derived from Rome, if only in terminology. The Twelve Tables of 451 BC are farmer law: fruit falling onto a neighbor's land, a cow eating someone else's grain, with a few goofy clauses about magic. Other early codes, including Hammurabi's, look similar and tend toward eye-for-eye justice. Rome's difference is that it kept writing. Jurists built theory; cases multiplied; in the sixth century Justinian compiled the lot, and that compilation became the base of later systems.

The fun of Roman law, he says, is the vignettes. A slave sent to a barber next to an athletic field dies when a missed ball hits the barber's hand and the razor opens the throat: is the thrower liable, the misser, the barber, the owner who chose that shop, or the state that zoned them together? There is no surviving verdict, only jurists commenting. A cow reportedly ran into an apartment, fell three stories into a bar, and kicked open the wine taps. About 20 percent of Roman law is testamentary: seven witnesses, a man of a specified role, adult males who are not blind. Floods that float furniture into the next building turn up in the cases Aldrete used for his book on Roman flooding. In the late Republic those courts were also a political theater, held in the open Forum, and Cicero made a career in them. Citizenship was the loaded idea: perhaps six million citizens among some fifty million inhabitants, a tiny minority, but "Civis Romanus sum" was supposed to stop a beating.

Roman slavery was not racial. A slave could be any color, origin, or gender; the status was economic. That does not soften the thing. A Roman agricultural writer, listing farm equipment, sorted tools into dumb ones that cannot speak, semi-articulate animals, and articulate tools, meaning slaves. Othering of that intensity, Aldrete says, is morally corrosive. The membrane was also permeable. A tombstone he likes records a man born free in Parthia, enslaved, freed, made a teacher, and dead a Roman citizen. War was the main source, with traders following the army; children of slaves and people sold by desperate fathers filled the rest. Agricultural slaves could be chained on plantations. Doctors, scribes, accountants, and barbers were often slaves too, trained as investments, sometimes allowed to buy freedom or freed in a will. In the city the worst hauling jobs might go to free laborers. Bronze collars in museums still read like dog tags: name, owner, reward for return. Under Roman law a runaway was guilty of theft, because he had stolen himself.

By about 100 BC the Republic had conquered the Mediterranean and looked triumphant. Almost every group inside it, Aldrete says, felt cheated. Veterans had fought while generals got rich and came home without land. Aristocrats outside a shrinking circle of families such as the Scipios felt locked out. Italian allies who had stayed loyal when Hannibal invaded wanted full citizenship and did not get it from a conservative state. Slaves worked the plantations that had eaten the old family farms. From 133 to 31 BC the late Republic is nearly constant internal strife, then civil war, a society at war with itself over how to share the profits of empire.

At the same time a chain of strong men put themselves above the state: Marius, Sulla, Pompey, Julius Caesar. Roman school stories had been about self-sacrifice. Marius made armies loyal to a general. Sulla marched on Rome and said it was for the state's good. Pompey held offices too young, raised private armies, and broke rules until he sided with the Senate under pressure. Caesar stopped pretending. Dictator was a legal office limited to six months; he made himself dictator for life, which is a king, and was killed for it. He had taken the state as one man. He had not solved how to rule that way and not look like a king. Arrogance did not help: he treated the Senate as inferiors and named a month after himself.

Caesar also knew how to play the people, putting on shows and presenting himself as their champion against a state that did not care, a dictator in populist clothing when it was convenient. Fridman calls the Gallic campaigns what they also were: a provoked war for one man's career, hundreds of thousands killed and enslaved across what is now France, Belgium, and part of Switzerland. Aldrete says calling Caesar a war criminal would not be unfair, and that scholarly fashion has swung with the century, from 1930s admiration of the strong man to postwar hatred of the dictator. Histories, he notes, often tell you more about the time they are written than about Caesar.

After the Ides there was a vacuum. Mark Antony, Caesar's lieutenant, looked like the obvious heir. Lepidus was a lesser version of the same. The Senate wanted its old weight back. Brutus and Cassius wanted control. Pompey's son Sextus seized Sicily and a navy. The dark horse was Caesar's grand-nephew, a seventeen-year-old named Octavian, a nobody until the will posthumously adopted him. The new name, Gaius Julius Caesar Octavianus, should not have mattered. Around the Mediterranean, about twelve hardened legions were used to following a man by that name. Overnight the eighteen-year-old had an army. Over the next decades he beat the field. He was, Aldrete stresses, a terrible general who lost almost every battle he commanded. He was a brilliant politician of image. He turned the war with Antony into a war against a foreign queen, Cleopatra, and an enemy of the Roman state.

Cleopatra was a descendant of Alexander's general Ptolemy, ten generations into a Macedonian dynasty that often married siblings, and apparently the first of them to bother learning Egyptian. She kept the last big independent kingdom on the Mediterranean alive by attaching herself first to Caesar, then, more convincingly in the stories of parties and god costumes, to Antony. Women in the sources are usually tagged as exceptions: one female philosopher, until you find sixty; one queen who led armies, until you find more; Eumachia of Pompeii with the largest building on the forum, until four other female guild patrons appear, plus Plancia Magna, a town's most important patron. Musa, a slave woman Augustus sent as a gift on an embassy to Parthia, became the king's concubine, then wife, murdered him, put her son on the throne, and ran an empire nearly Rome's size from behind the curtain. Traditional Roman-Parthian histories, Aldrete found while writing a lecture, often skip her and start with the son. The Prima Porta statue still boasts of the returned legionary eagles from that same diplomacy.

Once sole ruler, Octavian studied Caesar's mistakes. He lived in an ordinary house, wore a plain toga, ate simply, and treated the Senate with respect. He resigned the offices and had the Senate vote him their powers: a consul's command of armies and the Senate without being one of the two elected consuls, a tribune's veto without being a tribune. Elections continued. Off to the side sat a man whose power matched all the magistrates at once, with the army in his personal control. The titles were designed to be fuzzy. *Augustus* can mean deeply pious or itself divine. *Princeps* is first citizen, equal or superior depending on the stress. *Imperator*, a battlefield shout, became a permanent title and the root of emperor. He called the settlement a refounding of the Republic. His autobiography, the *Res Gestae*, is titled something like "stuff I did." The first line says that at eighteen, when a faction oppressed the Republic's liberty, he defended it. Aldrete's paraphrase: at eighteen he fought a civil war against another Roman and conquered the state.

Two accidents helped. He brought peace after nearly a century of civil war, so people who had lost family and property would take a killed Republic over dying in the streets. He seemed sickly and then ruled about fifty years, until almost no one alive remembered the old system. It took two hundred years, Aldrete says, before a Roman source bluntly called him a king. On his deathbed he asked, if he had played his part well, to be dismissed from the stage with applause. The mask was the point. He was also cruel when it paid: the triumviral proscriptions, Cicero among the dead, a slave tortured for angering him. Every later emperor took his titles. Charlemagne was crowned Charles Augustus, emperor of the Romans. Czars are Caesars; prince comes from *princeps*. That is the template of the good absolute ruler, and a mixed legacy, as Alexander's is mixed, because a lot of people started a lot of wars trying to be the next one.

Cicero was a *novus homo*, a new man without famous ancestors, a lousy general, not rich, not from a great house. He left more surviving words than almost any ancient author: philosophy, handbooks on speaking, volume after volume of private letters. He lived through the Republic's collapse and reached the highest office on one skill, getting up in front of a crowd and making them believe him. Public speaking was not a side craft at Rome. Courts, funerals, the Senate, the people, the games: if you could do this, you had a political career. Cicero was, some claim, as good as anyone has ever been.

His core bet was that people are ruled by emotion. Get a jury into fear or anger and facts, truth, evidence, and reason matter less. The toolkit is depressingly familiar: mudslinging, exaggeration, guilt by association, ad hominem attacks, name-calling, fear-mongering, us versus them. Human nature, Aldrete says, did not wait for modern consultants. Cicero also thought audiences were visual. He once delivered a defense cradling the defendant's newborn. Another time he parked a photogenic son behind him and talked about eyes brimming with tears; when there were no cute children, he produced the elderly parents. He had high talk about defending the Republic. He was not above the props.

Aldrete's dissertation started from a practical puzzle: no microphones, a windy Forum, ten or twenty thousand people. Voice training was part of it. So was a system of gestures. Combining Cicero's handbooks with about forty pages in Quintilian's *Institutio Oratoria*, he found that Roman oratorical signs did not map onto words the way American Sign Language does. A gesture marked the emotion you were supposed to feel. Romans even thought some hands would almost involuntarily produce the feeling. Cicero's metaphor is music. A horror scene gets strident cues; *Jaws* tenses the room; the orator's body is a lyre you learn to play. Pushing the hands aside is mild aversion; turning the face away makes it fear; a fist on the chest is anger or grief; a thigh slap is anger. Some signs are artificial: fingers curled in one by one, then flipped out, meant wonder.

Demosthenes, asked for the three most important things in a speech, said delivery, delivery, and delivery. Aldrete watches modern politicians the same way. Trump gesticulates a lot, but in a narrow set that punctuates rather than illustrates. Martin Luther King Jr. used the body creatively. So did Hitler; mute the newsreels and the emphasis is still there. The same techniques in King's hands look wonderful and in Hitler's look like a nation talked into atrocity. Done badly, gesture backfires. Cicero and Quintilian mock a speaker who seemed to swat flies, another who seemed to balance in a boat, and Titius, whose languid motions became a dance with his name. Too little is a problem, too much is a problem, and copying someone else's hands usually fails. It has to look natural, varied, and tied to the words.

For most of Roman history, Aldrete says, the working assumption was that lots of gods were floating around. You might like two of them; the neighbor might worship the oak in his yard; it was all legitimate. State cult prayed to certain gods on the state's behalf, but you were not executing Jupiter's will, and private life was not organized around a single demanding deity. Monotheism, once it dominates, flips that. There is one correct god, and religion moves from the auxiliary to the center of decision-making. Judaism, Christianity, and Islam, in his view, change how people place themselves in the world. Jesus was born under Augustus and crucified under Tiberius, a coincidence of political and religious force that Fridman lingers on.

The early clash with Christians looks, to Aldrete, almost like a failure of communication. Romans on the emperor's birthday said a prayer and sacrificed to the part of him that might become divine, which they treated as patriotism, a pledge of allegiance. Christians heard worship of another god. Hollywood likes a Rome obsessed with hunting believers for the first two hundred years. Aldrete thinks the state was mostly indifferent or ignorant. Around 100 AD, Pliny, a well-traveled governor, wrote to Trajan about people called Christians and described a weekly meeting where they swore not to do bad things and then ate breakfast, a garbled Ten Commandments and communion. If one of the best-educated officials in the empire knew basically nothing, not many people did. It looked like one more small mystery religion.

There were still reasons a Roman might have seen a threat. Rome cared about this world, citizenship, and status. Christianity pointed at the next world and said that in God's eyes a citizen and a slave, a man and a woman, were equal, a dangerous sentence in a hierarchy. It is no surprise, Aldrete says, that early converts included women and slaves, especially female slaves. In Pliny's letter the local leaders are two slave women called deaconesses, before any church structure exists. Three hundred years after Christ the emperor converted; another hundred years later, under Theodosius, Christianity became the official religion and pagans were the ones persecuted. For emperors facing endless usurpers, one god who picks one emperor is a legitimacy machine. For ordinary people the draw was a better afterlife than dust or a ghost in a grassy gymnasium, a claim of equal worth, and actual care for the sick and the poor.

Gladiators are Aldrete's exhibit of status dissonance: very low in one register, high in another. Most were slaves, often prisoners of war, using their bodies for other people's pleasure, which Romans found innately demeaning. Even hired labor looked suspect; the only truly noble work was farming, production for yourself. Successful fighters, though, became celebrities, admired, attractive. Movies that dump a crowd into the sand to die miss the economics. A scholar's sample of about a hundred fights with details found that roughly 10 percent ended in a death. The closer modern analogue is boxing: matched skill, likely survival, real risk. Schools had spent too much money to want the investment killed. Some men still refused. A German snapped his neck in a wagon wheel rather than fight. Twenty-nine others strangled one another the night before a show.

Why watch? A Roman line says a warlike people should be used to death. A symbolic reading treats the amphitheater as the empire in miniature, every rank gathered to decide the fate of foreigners, beasts, and criminals. The cynical reading is that people like violence: the hockey fight, the crash on the news. Fridman cites Dan Carlin's "Painfotainment" and the guess that a modern death-match, especially if anonymous, would still draw the world. Aldrete notes that some Romans at the time called the pleasure morally degenerate. There was no single ancient take. Exotic animals were another taste: an industry of capturing and shipping lions, elephants, giraffes, and rhinos so they could die in the city, draining parts of Africa in the process.

The building we call the Colosseum is the Flavian Amphitheater, raised around 80 AD by Vespasian on the site of Nero's Golden House. The message was deliberate: this dynasty serves Romans, not itself, paid for with loot from the sack of Jerusalem. It had retractable awnings, elevators and ramps from below, numbered passages for efficient crowds. Almost every later stadium, Aldrete says, owes it something. Rome's engineering genius was often humble. Shining marble was a facade over concrete. Strip the Colosseum and the structural core is what you see. Greeks built rectangles and forests of columns. Concrete let Romans pour curves and domes. The Pantheon still stands because the mix gets thicker and denser at the base and lighter toward the top, pumice where weight would hurt. Capitol buildings from Washington to Madison to Austin imitate that silhouette. Vitruvius wanted buildings that worked and pleased the eye. Two thousand years later, Aldrete wonders how many of ours will.

The cleverness of Augustus stops, in Aldrete's account, at the next man. He chose heredity, the nearest male relative, watched a series of young heirs die, and settled on Tiberius, a stepson he never liked. The Julio-Claudians then produced Caligula and Nero. The Flavians gave Vespasian and Titus, then Domitian, nuts again. In 98 AD, a century into the empire, Romans admitted the record was full of duds and did something their conservative habits rarely allowed: pick the best qualified adult and adopt him. Five emperors in about eighty years, Nerva through Marcus Aurelius, are the five good emperors, and the second century is often called the high point: Britain to Mesopotamia, Egypt to Germany, some fifty million people, relative peace inside the borders, a working if modest economy. Marcus Aurelius then looked around for the best man and found, coincidentally, his own son. Commodus followed. 180 AD is one of the earlier dates people pick for decline. Asked for a favorite Roman who was not an emperor, Aldrete names Marcus Agrippa, the childhood friend who won Actium, rebuilt much of Rome, put up the first Pantheon, cleaned sewers in person, and knew he lacked the front-man gift, so he took real power as number two and stopped. Without Philip II there is no Alexander; without Agrippa, Octavian never becomes emperor. If he has to pick an emperor, it is still Augustus, for the political savvy Agrippa did not have, not because he was a great human being.

Why so many mad emperors? Aldrete's working guess is age. Absolute power meets a personality that is not finished. The emperors later called good more often arrived in middle age. Augustus, who started as a teenager and did not go nuts, is the loud exception. Then he asks how much the emperor mattered. For a peasant in Spain, crazy Nero or solid Vespasian is mostly noise. The damage of a mad court stays within earshot: murdered senators and relatives, the occasional crowd thrown to the lions. The machine of governors still runs. War and taxes are the levers that reach everyone. Technology limits even those. A letter from Rome to Judea might take one or two months each way. Provinces had to decide and hope the emperor liked it, because four months of waiting is how you get nothing done. Instant talk across the world, Aldrete says, is something we can barely imagine living without.

Republican tax collection on overseas provinces was a bad auction. Private companies, the *publicani*, bid for the right to collect, paid the state up front, and squeezed the province for profit. The Bible's pairing of publicans and sinners, he notes, is a review. Later the system became more ordinary, often paid in wheat rather than coin. The economy was underdeveloped, and respectable Romans treated profit as shameful, hiding long-distance trade behind front men so the gentleman stayed a farmer on paper. After Marcus Aurelius, the historian Cassius Dio, who was there, wrote that the kingdom had descended from gold to rust and iron, a rare case of people naming decline in real time. The secret was out: the emperor is whoever commands the most swords. Generals declared themselves in threes and fours, raced to Rome, left borders empty, and invited raids. Civil war wrecked farms, taxes fell, winners raised rates, coinage was debased, and inflation followed. In 238, some eight or nine men passed through the job. It looked like the mid-third century would be the end. Army emperors pushed the borders back. Diocletian issued a guaranteed gold *solidus* and a price edict whose most expensive line, Aldrete notes with pleasure, is hiring a lawyer.

Constantine's conversion in the fourth century hit when Christians were perhaps 10 percent of the empire. He had used similar battlefield visions before, including Helios, and kept other gods on coins, so sincerity is a live argument; how well he understood the new religion may be the better question. The empire was also too big. Diocletian tried a tetrarchy of four; more often it simply split east and west. 476, when a barbarian king deposed Romulus Augustulus, is the famous Western date, but 410, 455, 180, 31 BC, and 1453 all have clients. Eastern Romans called themselves Romans, not Byzantines, with a legitimate claim. By around 500, Aldrete will say without being wishy-washy, whatever existed in the West was no longer the Roman Empire. Edward Luttwak's book on grand strategy started a fight over whether Romans even thought in frontiers. Virgil promised empire without end; Augustus already seemed to stop at the Rhine and Danube. Visigoths crossing the Danube look like invasion or, in newer language, migration and a request for asylum that Rome first bargained for and then bungled. Attila was stalled by a mixed Roman-barbarian coalition, then turned back from Rome after lunch with the Pope, saints with flaming swords in one set of sources, a bribe in another, and died on his wedding night. The blow Aldrete flags is the Vandals taking Spain and North Africa, the surplus-food engine of the city. Rome was no longer even the capital, the emperors having moved to swampy, defensible Ravenna, while Constantine's immodestly named Constantinople became the dominant city. Traditional blame is barbarian murder; other theories include Christianity, climate, plague from Marcus Aurelius onward, moral decay, which Aldrete doubts, and lead pipes, which he rejects because the same pipes ran while the empire expanded.

Aldrete's lecture series on decisive battles uses a simple test: did the fighting change who was in charge right away? Gaugamela is the type case. One afternoon, Darius III lost and the Persian Empire's ruler became a Macedonian. Other battles look decisive only later, when they let a people or an idea grow or stop an expanding empire cold. The Second Punic War is that kind of hinge for Rome. War is also a forced demonstration of new tools. World War II compressed the point: wood-and-wire biplanes to jets in four years, battleships treated as the measure of a navy and then as scrap beside carriers. The side that adapts faster tends to win, a story he says we have watched over and over.

He is a geographic determinist about the birth of civilization: Mesopotamia between rivers, the Nile, the Indus, the Yellow and Yangtze. Egyptian religion itself, in this view, grows out of a predictable flood. A professor once told him the best map of the Roman Empire is not political borders but the zone where olives can be grown in the first century AD, which tracks the most Romanized lands with uncomfortable closeness. About 80 percent of people in that world lived on olive oil, wine, and wheat. Romans defined civilization by those crops. A Greek administrator posted to northern Germany wrote home that the inhabitants led the most wretched life on earth because they grew neither olives nor grapes. The barbarian cliché was red meat, dairy, and beer, herders rather than farmers. Aldrete tells students in Green Bay that a time-traveling Roman, seeing the beer, sausage, and cheese, would know at once who they were. Under the diet is a whole life: farmers stay put and build cities; people who follow cattle do not.

Some Roman civil wars, he argues, were world wars in their own frame. The fighting after Caesar's murder ran through Spain, North Africa, Greece, Egypt, and Italy, seven or eight Roman factions, the whole world they knew. Adjust for travel time and he will say it was bigger than World War II: a week of hops from the United States to China then, a month from Spain to Egypt in antiquity. Nuclear weapons are the true novelty, the ability to end civilization wholesale, which Romans never had. Mutually assured destruction between two blocs was weirdly stable; a more crowded nuclear world, with China expanding its arsenal, unnerves him. What depresses the military historian is the refusal to learn. Afghanistan and the Hindu Kush have broken Alexander, the Mongols, the Huns, the Mughals, Victorian Britain, the Russians, and the Americans, on the same two mistakes: not reading rocky terrain full of caves, and not seeing that loyalty sits in tribes, not in a central government. He knows what happens next, and it still happens.

The book he wrote with his wife, *The Long Shadow of Antiquity*, is a list of how little of the present is free of the past, down to wedding habits and Julius Caesar's calendar of 365 days, twelve months, and leap years, which Pope Gregory only tweaked. You cannot make decent decisions now, he says, without knowing where you and other people came from. The hard part is the sources. A nineteenth-century topic would drown you; Roman literature of the main surviving kind fits on an eight-by-ten-foot office shelf, plus papyri, inscriptions, and dirt. Ninety-nine percent is gone, written by elite men, copied through centuries of telephone. His favorite warning is the nineteenth-century English-trained traveler who found ten-foot stone pairs with lintels in the North African desert, thought of Stonehenge, reconstructed Celtic blood rites, and had to be told by locals that they were looking at an old Roman olive press. If our world vanished, dorm-room Frisbees would become cult discs of the sun god Wham-O. Historians try to rebuild a picture faithful to the evidence, filtered through the sources' biases and their own, then revise like scientists or detectives. Livy said history offers noble things to imitate and shameful things to avoid. What gives Aldrete hope is curiosity, and the human trick of storing knowledge so the next generation does not start at zero.