Ancient Persia's Conquest of Egypt

As Egypt was torn by Civil War, with those fighting for a return of the Old Kingdom, and those pushing for the acceptance of foreigners as powerful members of the government, Persia was quickly building an empire.
Led by Cyrus the Great, the Persians conquered Babylon, then, with their newly gained armies' help, sacked Nineveh, capital of Assyria. With this newfound power, Persia sent Cambyses, son of Cyrus II (his relation to Cyrus the Great can only be presumed) to conquer Egypt.
In approximately 525 BC, Cambyses began his assault on Egypt with the victory at Pelsium. He continued into the country until arriving at the Pharaoh's city, Memphis. Cambyses went to lay siege on the city, and, after this final victory, had the Pharaoh, Psammetichus III, executed (Another source has it as the Pharaoh Amasis being executed [David, 1975]).
After the death of Psammetichus, Cambyses becomes the first ruler of the 27th Dynasty. As the Greek observer Herodotus has it, Cambyses was a sacrilegious, evil king. Cambyses then pronounces Egypt as a Satrapy (state) of the Persian empire, himself the satrap (Governor). However, he is eventually forced back to the Persia, leaving Egypt behind (Again, other sources suggest he returned to the Asian conquests by his choice [David, 1975]). After his leave, Darius I takes over, and, contrary to Cambyses, sees Egypt not as a Satrapy but it's own kingdom, and makes himself it's Pharaoh. Throughout his reign he shows continual interest in Egypt's ways, to the point of adopting its religion as his own.