190 BC

Battle of Magnesia

Roman and Pergamene forces defeat Antiochus III at Magnesia

Eumenes beat the scythed chariots by frightening their horses. The weapons meant to cut through Roman ranks tore into the Seleucid line instead.

December or January: the date is unresolved

Ancient evidence preserves no universally accepted calendar date. Modern scholarship places the battle late in 190 BCE, commonly in December, but January 189 BCE remains an alternative because Roman civic chronology is hard to align with the Julian calendar.

The site is Magnesia ad Sipylum, near modern Manisa — not Magnesia on the Maeander.

Appian reports about 30,000 Roman and allied troops against 70,000 Seleucids, including a 16,000-strong phalanx; those are literary figures, not audited headcounts.

Antiochus won his wing and lost the battle

Eumenes II of Pergamon, commanding the allied right, sent dispersed archers, slingers and javelin throwers against the Seleucid scythed chariots. The wounded horses bolted into their own side and disrupted the Seleucid left.

Antiochus III personally broke the Roman left — not the right, as accounts often have it — and pursued the fugitives toward their camp. There the tribune Marcus Aemilius rallied them while reinforcements arrived from the victorious allied right.

The phalanx did not crumple on contact. It held until missile fire panicked the elephants embedded within it and broke the formation; the Romans then took the Seleucid camp.

Surrenders first, treaty two years later

Antiochus fled and reached Sardis around midnight. The next day delegations from nearby cities began offering surrender, among them Magnesia, Thyatira, Sardis, Tralles and Ephesus.

Livy puts Seleucid losses at 50,000 infantry and 3,000 cavalry killed with 1,500 prisoners, against 300 Roman infantry, 24 Roman cavalry and 25 of Eumenes's troops.

Nothing was signed on the battlefield: preliminary negotiations and a truce intervened, and the Treaty of Apamea followed in 188 BCE.

Sources

Researched 24 Aug 2026 6 sources not yet audited Date disputed

How this was checked

Researched from the web into a fact sheet and rewritten from that sheet. This article has not yet had an independent model audit. How the pipeline works →

Date disputed. Sources disagree; the research places it at ~-0190-12.

What the sources leave uncertain

Ancient evidence does not preserve a universally accepted calendar date.
Modern scholarship places the battle late in 190 BCE, commonly in December, but January 189 BCE remains an alternative because of problems aligning Roman civic chronology with the Julian calendar.
The enormous army and casualty totals come from ancient literary narratives and should be presented as reported figures, not audited headcounts.