The Cilician pirates had not been completely defeated, and Mithridates signed an alliance with them. He was also allied with the government of Quintus Sertorius in Spain and with his help reorganized some of his troops in the Roman legionary pattern with short stabbing swords. The Third Mithridatic war broke out when NicomedesIV of Bithynia died without heirs in 75 and left his kingdom to Rome. In 74BCE Rome mobilized its armies in Asia Minor, probably provoked by some move made by Mithridates, but our sources are not clear on this. In 73 Mithridates invaded Bithynia, and his fleet defeated the Romans off Chalcedon and laid siege to Cyzicus. Lucullus marched from Phrygia with his five legions and forced Mithridates to retreat to Pontus. In 72BCE Lucullus invaded Pontus through Galatia and marched north following the river Halys to the north coast, he besieged Amisus, which withstood until 70BCE. In 71 he marched through the Iris and Lycus river valleys and established his base in Cabeira. Mithridates sent his cavalry to cut the Roman supply line to Cappadocia in the south, but they suffered heavy casualties. Mithridates, still unwilling to fight a decisive engagement, now began a retreat to Lesser Armenia, where he expected aid from his ally Tigranes the Great. Because of his now weakened cavalry, the retreat turned into an all-out rout, and most of the Pontic army was destroyed or captured. These events led Machares, the son of Mithridates and ruler of the Crimean Bosporus, to seek an alliance with Rome. Mithridates fled to Armenia. In the summer of 69 Lucullus invaded Armenian territory, marching with 12,000 men through Cappadocia into Sophene. His target was Tigranocerta, the new capital of Tigranes's empire. Tigranes retreated to gather his forces. Lucullus laid siege to the city, and Tigranes returned with his army, including large numbers of heavily armored cavalrymen, termed Cataphracts, vastly outnumbering Lucullus' force. Despite this, Lucullus led his men in a charge against the Armenian horses and won a great victory at the Battle of Tigranocerta. Tigranes fled north while Lucullus destroyed his new capital city and dismantled his holdings in the south by granting independence to Sophene and returning Syria to the Seleucid king Antiochus XIII Asiaticus.