After the collapse of the Old Kingdom, Egypt entered a period of weak pharaonic power and decentralization called the First Intermediate Period.[3] Towards the end of this period, two rival dynasties, known in Egyptology as the Tenth and Eleventh, fought for control of the entire country. The Theban Eleventh Dynasty only ruled southern Egypt from the First Cataract to the Tenth Nome of Upper Egypt. To the north, Lower Egypt was ruled by the rival Tenth Dynasty from Herakleopolis.[4] The struggle was to be concluded by Mentuhotep II, who ascended the Theban throne in 2055 BC.[5] During Mentuhotep II's fourteenth regnal year, he took advantage of a revolt in the Thinite Nome to launch an attack on Herakleopolis, which met little resistance.[4] After toppling the last rulers of the Tenth Dynasty, Mentuhotep began consolidating his power over all of Egypt, a process which he finished by his 39th regnal year.[3] For this reason, Mentuhotep II is regarded as the founder of the Middle Kingdom.[6]