Egyptian civilization coalesced around 3150 BC with the political unification of Upper and Lower Egypt under the first pharaoh. The history of ancient Egypt occurred in a series of stable Kingdoms, separated by periods of relative instability known as Intermediate Periods. The Old Kingdom of the Early Bronze Age, the Middle Kingdom of the Middle Bronze Age and the New Kingdom of the Late Bronze Age. Egypt reached the pinnacle of its power during the New Kingdom, in the Ramesside period, after which it entered a period of slow decline. Egypt was conquered by a succession of foreign powers in this late period. In the aftermath of Alexander the Great's death, one of his generals, Ptolemy Soter, established himself as the new ruler of Egypt. This Ptolemaic Dynasty ruled Egypt until 30 BC, when it fell to the Roman Empire and became a Roman province.