Egypt reached the pinnacle of its power during the New Kingdom, in the Ramesside period where it rivalled the Hittite Empire, Assyrian Empire and Mitanni Empire, after which it entered a period of slow decline. Egypt was invaded or conquered by a succession of foreign powers, such as the Canaanites/Hyksos, Libyans, the Nubians, the Assyrians, Babylonians, the Achaemenid Persians, and the Macedonians in the Third Intermediate Period and the Late Period of Egypt. In the aftermath of Alexander the Great's death, one of his generals, Ptolemy Soter, established himself as the new ruler of Egypt. This Greek Ptolemaic Kingdom ruled Egypt until 30 BC, when, under Cleopatra, it fell to the Roman Empire and became a Roman province.
The success of ancient Egyptian civilization came partly from its ability to adapt to the conditions of the Nile River valley for agriculture. The predictable flooding and controlled irrigation of the fertile valley produced surplus crops, which supported a more dense population, and social development and culture. With resources to spare, the administration sponsored mineral exploitation of the valley and surrounding desert regions, the early development of an independent writing system, the organization of collective construction and agricultural projects, trade with surrounding regions, and a military intended to defeat foreign enemies and assert Egyptian dominance. Motivating and organizing these activities was a bureaucracy of elite scribes, religious leaders, and administrators under the control of a pharaoh, who ensured the cooperation and unity of the Egyptian people in the context of an elaborate system of religious beliefs.