Some of Egypt’s greatest statuary, art and literature was produced during this era (c. 2000–1523 BCE). It began with reunification and ended with enemy occupation. Amenemhat I (the first pharaoh of the Middle Kingdom) and his successors ruled Egypt for 200 years. Amenemhat, I moved the capital from Thebes to Memphis and is thought to have built the’ Walls of the Ruler’, a huge set of military fortifications in the Nile delta. His successor, Senusret I, created Egypt’s first standing army, improved the country’s infrastructure and implemented large building projects, including his pyramid complex at El-Lisht. The kingdom was at its height under Sensuret III who campaigned in Palestine and invaded and fortified Nubia. Over time, Egypt weakened under a succession of ephemeral kings. The eastern delta established a separate kingdom. Finally, Egypt was invaded and occupied by the Asiatic Hyksos (c. 1630–1523 BCE).