Alexander's generals, known as diadochi, jostled for supremacy over parts of his empire following his death. Ptolemy I Soter, a former general and then current satrap of Egypt, was the first to challenge the new system, which eventually led to the demise of Perdiccas. Ptolemy's revolt created a new subdivision of the empire with the Partition of Triparadisus in 320 BCE. Seleucus, who had been "Commander-in-Chief of the Companion cavalry" (hetairoi) and appointed first or court chiliarch (which made him the senior officer in the Royal Army after the regent and commander-in-chief Perdiccas since 323 BCE, though he helped to assassinate him later) received Babylonia and, from that point, continued to expand his dominions ruthlessly. Seleucus established himself in Babylon in 312 BCE, the year later used as the foundation date of the Seleucid Empire.