With Hyrcanus established, Antipater thrived and laid the foundation for his family's success by navigating conflicts of loyalty and power-shifting within the Roman elite. When Julius Caesar and Pompey went to war in 49/48 BCE, Antipater at first sided with Pompey, when the latter was defeated by Caesar, Antipater shifted his allegiance to Caesar. While Caesar was besieged in Alexandria, Antipater and Mithridates of Pergamon rescued him with 13,000 men and the aid of numerous nearby friends. For his "demonstrations of valor" Caesar elevated Antipater to Roman citizenship, freed him from taxes, and showered him with honors and declarations of friendship.