First, Tsongkhapa established three great monasteries around Lhasa in the province of Ü before he died in 1419. The 1st Dalai Lama soon became Abbot of the greatest one, Drepung, and developed a large popular power base in Ü. He later extended this to cover Tsang, where he constructed a fourth great monastery, Tashi Lhunpo, at Shigatse. The 2nd studied there before returning to Lhasa, where he became Abbot of Drepung. Having reactivated the 1st's large popular followings in Tsang and Ü, the 2nd then moved on to southern Tibet and gathered more followers there who helped him construct a new monastery, Chokorgyel. He also established the method by which later Dalai Lama incarnations would be discovered through visions at the "oracle lake", Lhamo Lhatso. The 3rd built on his predecessors' fame by becoming Abbot of the two great monasteries of Drepung and Sera. The stage was set for the great Mongol King Altan Khan, hearing of his reputation, to invite the 3rd to Mongolia where he converted the King and his followers to Buddhism, as well as other Mongol princes and their followers covering a vast tract of central Asia. Thus most of Mongolia was added to the Dalai Lama's sphere of influence, founding a spiritual empire which largely survives to the modern age. After being given the Mongolian name 'Dalai', he returned to Tibet to found the great monasteries of Lithang in Kham, eastern Tibet and Kumbum in Amdo, north-eastern Tibet. The 4th was then born in Mongolia as the great grandson of Altan Khan, thus cementing strong ties between Central Asia, the Dalai Lamas, the Gelugpa and Tibet. Finally, in fulfilment of Avalokiteśvara's master plan, the 5th in the succession used the vast popular power base of devoted followers built up by his four predecessors. By 1642, a strategy that was planned and carried out by his resourceful "chagdzo" or manager Sonam Rapten with the military assistance of his devoted disciple Gushri Khan, Chieftain of the Khoshut Mongols, enabled the 'Great 5th' to found the Dalai Lamas' religious and political reign over more or less the whole of Tibet that survived for over 300 years.