Gregory Aldrete on Ancient Rome, the Roman Legions, and Military History

Gregory Aldrete on Ancient Rome, the Roman Legions, and Military History

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Gregory Aldrete on Ancient Rome, the Roman Legions, and Military History

Gregory Aldrete — historian of ancient Rome, University of Wisconsin-Green Bay — speaks with Lex Fridman about Rome’s three phases, its integration formula, Hannibal at Cannae, the Roman legion vs the Macedonian phalanx, his experimental linothorax armour project, Roman law, Roman slavery, Alexander the Great’s success and failure, and the fall of the Republic.

Source: Lex Fridman Podcast

Key ideas

  • Integration was Rome’s decisive advantage. Conquered cities provided troops; auxiliaries became citizens; barbarian sons became Roman. The formula that defeated Hannibal (Italian allies didn’t rebel) is the same formula that sustained centuries of empire.
  • Cannae was Rome’s darkest hour and its turning point. 60,000 killed in one afternoon — more than Americans in 20 years of Vietnam. Rome survived, regenerated, and became unbeatable. Hannibal’s strategy required allied defection that never came.
  • Roman tactical flexibility defeated the phalanx. The Macedonian sarissa-phalanx was unstoppable head-on; the Roman legion’s subdivision into manoeuvrable cohorts enabled flanking attacks that the phalanx couldn’t counter.
  • Structure outlasts charisma. Alexander built an empire on personal loyalty and left no succession plan; it fragmented immediately. Rome built institutions — law, citizenship, incorporation — that transferred power without collapse.
  • Roman law is the ancient world’s most durable legacy. ~90% of world legal systems derive from Roman jurisprudence; Justinian’s Code compiled in the 6th century AD is the direct ancestor.

Ancient world vs modern world

Human nature is roughly constant across history — tombstones and letters reveal that people 2,000 years ago experienced the same fears, loves, and griefs. The structural differences are technology and child mortality (~30–40% before puberty in the ancient world). In the ancient world, 9 in 10 people were small family farmers.

Romans were obsessed with the past in ways moderns are not. Aristocratic families kept wax death masks of ancestors in cabinets by the front door; children memorised ancestors’ accomplishments. This mos maiorum — “way of the ancestors” — governed Roman life. It was “obsessive and oppressive.” It determined what one could and couldn’t do. Five hundred years after the Romans expelled their last king, graffiti appeared asking Brutus to remember his ancestor — compelling him to assassinate his closest friend to uphold the Republican precedent.

Three phases of Roman history

  1. Monarchy (753–509 BC): Rome was mostly mud huts; influenced heavily by the Etruscans (toga, gladiatorial games, much of Roman religion — not originally Roman).
  2. Republic (509–27 BC): ~500 years; expansion from a city-state to Italy to the entire Mediterranean basin. The Senate, consuls, and assemblies balanced power. Mos maiorum governed conservative political culture.
  3. Empire (27 BC–476 AD Western; 1453 AD Eastern): Augustus’s Principate masking autocratic rule under Republican forms.

Integration formula

Rome’s early military success was manpower, not technology: conquered Italian cities provided troops, not tribute. Pyrrhus — a Greek mercenary king — defeated Rome three times and called it “fighting a hydra.” Hannibal’s Second Punic War strategy correctly identified the vulnerability: cut Rome’s Italian allies. It failed because the Italian communities, already incorporated into the Roman project, declined to rebel.

Later, this integration scaled to the empire: barbarian chiefs’ sons educated in Rome; auxiliaries (non-citizen soldiers) earning citizenship after 25 years of service; their children enlisting as legionaries. By the 2nd century AD, emperors came from Spain, North Africa, and Syria. “The Roman military — half a million people — takes foreigners and churns out Romans.”

Punic Wars: Hannibal and Cannae

Hannibal Barca — Carthage’s supreme military commander — crossed the Alps with elephants (218 BC), destroyed two Roman armies, and drew 80,000 Romans into battle at Cannae (216 BC). His double envelopment is the most famous tactical manoeuvre in ancient history:

  • Weaker infantry in the centre absorb and retreat under Roman pressure, pulling the legions inward
  • Superior cavalry on the flanks rout Roman cavalry, then encircle from behind
  • Romans are packed too tight to fight, panic, and are slaughtered

~60,000 Romans died in one afternoon. “More Romans died at Cannae than Americans in 20 years in Vietnam. More than Gettysburg’s three-day death toll.” Rome was at its lowest point. But it raised new armies rather than suing for peace, attacked Carthaginian holdings in Spain, and eventually Scipio Africanus crossed into North Africa. Hannibal, undefeated in Italy for 12 years, was recalled and defeated at Zama (202 BC). Carthage fell.

The double envelopment — Cannae’s legacy — became the template for encirclement throughout military history, including the German Blitzkrieg and Gulf War manoeuvres.

Roman legion vs Macedonian phalanx

The Macedonian sarissa system (15-foot pikes, deep formation) was unstoppable head-on but rigid on flanks. Alexander’s phalanx was a single 5,000-man unit. The Roman innovation: subdivision into flexible cohorts (8-man contuberniae → 80-man centuries → cohorts → legions). At the 197 BC Battle of Cynoscephalae, Romans broke off cohorts mid-battle to flank and attack the phalanx from the rear — exactly its fatal vulnerability. Tactical flexibility defeated frontal power.

Linothorax: experimental archaeology

Linothorax — linen armour laminated with animal glue — was standard Greek and Macedonian armour of the 5th–4th centuries BC. No example survives. Aldrete’s project: 65 literary sources, ~1,000 images in ancient art, reconstruction using ancient materials (hand-spun linen, rabbit glue), ballistics testing with replica arrows and genuine bronze arrowheads.

Result: 1 cm of linothorax ≈ 2 mm bronze protection, stopping random arrow strikes. Weight: 11 lbs vs 24–26 lbs for bronze cuirass, 27–28 lbs for chainmail. It was lighter, cooler, and cheaper — any household could make it without a specialist blacksmith. Eventually superseded by composite bows and sharper steel arrowheads that defeated fabric armour.

Alexander the Great

Alexander succeeded through combination of: inherited instrument (Philip II’s Macedonian army), personal charisma and tactical intelligence, multi-element combined-arms warfare, and a vision of cultural fusion rather than simple conquest. He failed at succession — his empire was personal, not institutional. It fragmented immediately on his death. Rome’s longevity derives from the opposite: institutional structure that transfers power without catastrophic loss.

Roman law

The Twelve Tables (c. 451 BC) were crude agrarian law: who owns fruit that falls on a neighbour’s land? By the late Republic, Roman law had expanded into a vast body of cases and theoretical commentary. Emperor Justinian’s 6th-century codification (Corpus Juris Civilis) is the basis for ~90% of legal systems worldwide.

Key innovation: citizenship as a legal status with real protections. “Civis Romanus Sum” — “I am a Roman citizen” — was a phrase that demanded due process. Late Republic law became public spectacle: cases held in the open Forum, audiences entertained by oratory. Cicero’s entire political career was built on legal rhetoric.

Roman slavery

Not racial — slaves were of all backgrounds, primarily war captives. Categorised in Roman agricultural writing as “articulate tools” alongside animals and shovels. Under law, a runaway slave was guilty of theft — having stolen himself. Yet the institution was permeable: skilled slaves could buy freedom; masters freed slaves in wills; the same person could move from free to slave to citizen across one lifetime.

Fall of the Republic and Augustus

The Republic fell because mos maiorum prevented the structural reforms Rome needed as the empire expanded. Powerful generals accumulated personal armies; Caesar crossed the Rubicon. Augustus solved the problem by maintaining Republican forms (Senate, magistrates) while concentrating power — the Principate, a fiction of restored Republic masking autocracy. Unlike Alexander, Augustus built institutions that survived him.