Antiochus III the Great vs Valentinian I

Antiochus III defeated Ptolemy IV's army at Raphia in the largest battle of the Syrian Wars. He used war elephants and a phalanx of native Egyptians to secure victory, recapturing Coele-Syria and Palestine from Ptolemaic control, restoring Seleucid power in the region.

Antiochus III led a major military expedition to the eastern satrapies of the Seleucid Empire, including Parthia, Bactria, and India. He reasserted Seleucid authority, received tribute from local rulers, and secured the eastern borders, earning the title 'the Great'.

Antiochus III invaded Greece, leading to war with the Roman Republic. He was decisively defeated at the Battle of Thermopylae (191 BC) and the Battle of Magnesia (190 BC) by Roman forces under Scipio Asiaticus, ending Seleucid ambitions in Europe and Asia Minor.

Antiochus III signed the Treaty of Apamea with Rome, ending the war. He surrendered all territory in Asia Minor west of the Taurus Mountains, paid a massive indemnity of 15,000 talents, and agreed to limit his navy and war elephants, crippling Seleucid power.

Antiochus III was killed while attempting to plunder the temple of Bel in Elymais (southwestern Iran) to raise funds for the Roman indemnity. His death marked the end of Seleucid resurgence and the beginning of the empire's decline.

After the sudden death of Jovian, the Roman army elected Valentinian I as emperor at Nicaea. Valentinian was a capable military officer from Pannonia. He immediately appointed his brother Valens as co-emperor for the East, dividing the empire.

Valentinian I launched a series of campaigns against the Alamanni tribes who had invaded Gaul. He crossed the Rhine River and defeated them at the Battle of Solicinium (modern Rottenburg am Neckar). These campaigns secured the Rhine frontier for a decade.

Valentinian I ordered an extensive program of fortification along the Rhine and Danube borders. He built new forts, repaired existing walls, and established a system of watchtowers. This defensive strategy strengthened Roman control and deterred barbarian raids.

While receiving a delegation of Quadi barbarians at Brigetio on the Danube, Valentinian I became enraged at their insolent demeanor. He suffered a stroke (apoplexy) and died shortly after. His sudden death left the Western Empire in the hands of his young sons Gratian and Valentinian II.