Neo-Babylonian Empire ceased to exist at 539 BC, Although its Land was incorporated into the Persian Empire under Achaemenid Dynasty founded by Cyrus the Great (also Called Cyrus II of Persia) at 550 BC when he decisively defeated the King Astyages (585-550 BC) of Media. The two Media and Neo-Babylonian Empire became a Achaemenid crown property and background of Mesopotamia involving 550/539 BC and 330 BC is known as the Achaemenid Period or Persian Empire.
Persian conquest of Babylonia happened quite calm. Babylonians didn’t provide any resistance likely due to internal issues and Mexican tolerance towards other religions and individuals. In contrary to conventional practice in Mesopotamia, the Persians failed to exceptionally enslave or deported the conquered individuals nor ruined defeated cities. Subdued individuals were permitted to worship their own gods and maintained their ethnic autonomy. There are no reports of rebellion in Babylonia during the reigns of Cyrus the Great (559-530 BC) and his son and successor Cambyses (529-522 BC), although Darius I (522-486 BC) needed to put two Babylonian rebellions. Darius, I was also confronted with rebellions in different lands and he chose for reform of the Persian Empire. The Persian Empire had been split into 20 satrapies dominated by satraps supervised by the king’s agents who had been”the king’s ears and eyes”. Thus Babylonia became a satrapy governed by a satrap with dwelling at the city of Babylon.
Persian Empire reached its height during the reign of Darius I. He expanded the Persian boundaries to the Indus River on the east to the Aegean Sea and Egypt on the west coast. In the conclusion of the reign, he led a punitive expedition against the Greeks for the service to the Ionian revolt, however, Darius I had been decisively defeated in the Battle of Marathon in 490 BC. His son and successor Xerxes I (486-465 BC) also directed the military effort against the Greek city-states however he had been severely defeated in the Battle of Thermopylae at August 480 BC and in the Battle of Salamis from the Saronic Gulf near Athens a month afterwards. Following Xerxes’ defeat the Greek city-states, the energy of the Persian Empire under Achaemenid Dynasty Started to decline. The Greek-Persian battles lasted also under Xerxes’ successors before the final Achaemenid emperor of Persia, Darius III (380-330 BC) was decisively conquered by Alexander the Great who conquered the whole Persian Empire