The battle that destroyed the Roman Republic was fought on the plain of Pharsalus in Thessaly on August 9, 48 BC. Pompey had a significant numerical advantage — perhaps 45,000 infantry to Caesar's 22,000 and 7,000 cavalry to Caesar's 1,000. His plan was simple: use his overwhelming cavalry on the left wing to sweep away Caesar's horsemen, then envelop the Caesarian infantry from the rear. Caesar anticipated exactly this and placed six secretly withdrawn cohorts behind his cavalry with orders to advance obliquely when the Pompeian horse charged. The plan worked precisely: Pompey's cavalry, unused to infantry counter-attacking from unexpected angles, broke and fled. The six cohorts then wheeled into the Pompeian infantry's unprotected flank. Caesar's veteran infantry, advancing simultaneously from the front, completed the encirclement. The Pompeian army collapsed entirely; Pompey fled the battlefield without giving any orders, according to Caesar's own account. Caesar reported 15,000 Pompeians killed and 24,000 prisoners; his own losses were 200 soldiers and 30 centurions.
Pharsalus was the single most decisive battle of the Roman Civil Wars and one of the most consequential battles in world history. It ended Pompey's military power in a single afternoon, established Caesar as the uncontested master of the Roman world, and made the survival of the Republic politically impossible. The word 'Pharsalia' became synonymous in Latin with utter defeat.
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Two years after the Goths were admitted across the Danube as refugees and then driven to revolt by Roman mistreatment, the Eastern emperor Valens attacked Fritigern's Gothic host outside Adrianople without waiting for reinforcements. Gothic cavalry, returning unexpectedly, smashed into the Roman flank; the legions were surrounded and annihilated on the field. Valens himself was killed, his body never recovered.
Adrianople was the worst Roman defeat in centuries — the historian Ammianus compared it to Cannae. The destruction of an entire field army and the death of an emperor at barbarian hands shattered the myth of Roman invincibility, forced Rome to settle the Goths inside the empire as semi-autonomous allies, and is often taken as the opening catastrophe of the long fall of the West.
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The Battle of Coamo was one of the most tactically interesting engagements of the Puerto Rico campaign. Brigadier General James Wilson planned a double envelopment of the Spanish defensive position at Coamo, a mountain town in the island's interior. While a frontal force fixed the Spanish defenders' attention, a flanking column swung around through the hills to cut off their retreat. The maneuver worked almost perfectly. The Spanish garrison was surprised, their line of retreat cut, and the town fell quickly. The action demonstrated the improving tactical skill of American volunteer forces over the course of the brief campaign.
Coamo was the most complete tactical victory of the Puerto Rico campaign and accelerated the advance toward the Spanish capital at San Juan. The battle showed that American volunteer forces could execute complex flanking maneuvers under campaign conditions.
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The introduction of internment without trial saw hundreds of nationalist men rounded up and imprisoned, almost none of them loyalists, in a one-sided policy that inflamed the Catholic community. During the operation, soldiers of the Parachute Regiment shot dead eleven civilians in the Ballymurphy area of Belfast over three days, an atrocity that fed a surge of recruitment into the Provisional IRA.
Internment was a catastrophic misjudgement that alienated the nationalist population, drove young men into the IRA, and pushed the conflict toward its bloodiest phase. Ballymurphy prefigured the far more infamous killings at Derry five months later.
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