The ancient Greek city-states on some occasions dispatched envoys to negotiate specific issues, such as war and peace or commercial relations, but did not have diplomatic representatives regularly posted in each other's territory. However, some of the functions given to modern diplomatic representatives were fulfilled by a "proxenos", a citizen of the host city who had friendly relations with another city, often through familial ties. In times of peace, diplomacy was even conducted with non-Hellenistic rivals such as the Achaemenid Empire of Persia, through it was ultimately conquered by Alexander the Great of Macedon. Alexander was also adept at diplomacy, realizing that the conquest of foreign cultures were be better achieved by having his Macedonian and Greek subjects intermingle and intermarry with native populations. For instance, Alexander took as his wife a Sogdian woman of Bactria, Roxana, after the siege of the Sogdian Rock, in order to placate the rebelling populace. Diplomacy remained a necessary tool of statecraft for the great Hellenistic states that succeeded Alexander's empire, such as the Ptolemaic Kingdom and Seleucid Empire, which fought several wars in the Near East and often negotiated peace treaties through marriage alliances.