The third war of the Diadochi broke out because of the growing power and ambition of Antigonus. He began removing and appointing satraps as if he were king and also raided the royal treasuries in Ectabana, Persepolis and Susa, making off with 25,000 talents. Seleucus was forced to flee to Egypt and Antigonus was soon at war with Ptolemy, Lysimachus, and Cassander. He then invaded Phoenicia, laid siege to Tyre, stormed Gaza and began building a fleet. Ptolemy invaded Syria and defeated Antigonus' son, Demetrius Poliorcetes, in the Battle of Gaza of 312 BC which allowed Seleucus to secure control of Babylonia, and the eastern satrapies. In 310, Cassander had young King Alexander IV and his mother Roxane murdered, ending the Argead Dynasty which had ruled Macedon for several centuries.