Battle of Sellasia 222 BC
See other thread. Achaian League & Macedon in the plain attacking two Spartan armies on two fortificated hills.
Battle of Zela August 2, 47 BC
Pontos vs Rome. On his way back from Egypt Gaius Julius Caesar faced a rebellion of Mithridates' son Pharnaces II against Roman overrule. Pharnaces was able to - perhaps the only person ever to do so- take Caesar by surprise and attacked the Roman lines while they were still forming on a hill position. But the legionary lines, together with their feroucious Galatian mercenary allies, held firm and repelled the attack, crushing both the Pontic army and Pharnaces' dreams of rebuilding his father's empire at once. After the battle, Caesar set down and wrote a letter to his friend Amantius in Rome, describing the events laconically: ,, Veni, vidi, vici.''