The Battle of Magnesia (190 B.C.) was the concluding battle of the Syrian War
. It was fought between a consular army of the Romans under L. Cornelius Scipio and Scipio Africanus
, with about 3000 Greeks and about 800 men from their ally Eumenes II of Pergamum, against the Seleucid monarch
Antiochus III who commanded an army more than twice the size of the Roman one. His army was based on the Greek phalanx and included war elephants. The Romans were a superior fighting force, the phalanx was unwieldy, and the elephants stampeded. Antiochus fled, leaving more than 50,000 of his men slain on the field. Antiochus lost all his conquered territory in Asia Minor
. In the peace treaty known as the Peace of Apamea, Antiochus was forced to pay a large tribute then and for the next 12 years, to give up his elephants and warships, and more. One of the additional terms was that he was to surrender Hannibal
to the Romans, but that didn't happen.
Just as one of the Scipio brothers was named Africanus because of his victory in the Hannibalic war, so his brother, the consul L. Cornelius Scipio took on the name Asiaticus for his victory.
It's called the Battle of Magnesia because it was fought near Magnesia ad Sipylum, in Lydia.
Ancient historical sources include Livy and Appian.
Main References: A history of Rome: from the earliest times to the establishment of the Empire, by Henry George Liddell (1858) and Rickard, J (9 November 2008), Battle of Magnesia, December 190 B.C., http://www.historyofwar.org/articles/battles_magnesia.html