For 70 peaceful years Byang-chub rgyal-mtshan (died 1364) and his two successors ruled a domain wider than that of the Sa-skya-pa. Thereafter, although the Phag-mo-gru Gong-ma (as the ruler was called) remained nominally supreme, violent dissension erupted again. In 1435 the lay princes of Rin-spungs, ministers of Gong-ma and patrons of the increasingly influential Karma-pa sect, rebelled and by 1481 had seized control of the Phag-mo-gru court.

Already a new political factor had appeared in the Dge-lugs-pa sect. Its founder was a saintly scholar, Blo-bzang grags-pa (died 1419), known, from his birthplace near Koko Nor, as Tsong-kha-pa. After studying with leading teachers of the day, he formulated his own doctrine, emphasizing the moral and philosophical ideas of Atisha rather than the magic and mysticism of Sa-skya--though he did not discard the latter entirely. In 1409 he founded his own monastery at Dga'-ldan, devoted to the restoration of strict monastic discipline. Tsong-kha-pa's disciplinary reform appealed to people weary of rivalry and strife between wealthy monasteries. Tsong-kha-pa probably did not imagine that his disciples would form a new sect and join in that rivalry, but, after his death, devoted and ambitious followers built around his teaching and prestige what became the Dge-lugs-pa, or Yellow Hat sect, which was gradually drawn into the political arena.

In 1578 the Dge-lugs-pa took a step destined to bring foreign interference once more into Tibetan affairs. The third Dge-lugs-pa hierarch, Bsod-nams-rgya-mtsho, was invited to visit the powerful Tümed Mongol leader Altan Khan, with whom he revived the patron-priest relationship that had existed between Kublai Khan and 'Phags-pa. From this time dates the title of Dalai ("Oceanwide") Lama, conferred by Altan and applied retrospectively to the two previous hierarchs. The holder is regarded as the embodiment of a spiritual emanation of the bodhisattva-- Avalokiteshvara, the mythic monkey demon and progenitor of the Tibetans. The succession is maintained by the discovery of a child, born soon after the death of a Dalai Lama, into whom the spirit of the deceased is believed to have entered. Until 1642 the Dalai Lamas were principal abbots of the Dge-lugs-pa, and in that year they acquired temporal and spiritual rule of Tibet. With Altan's help virtually all the Mongols became Dge-lugs-pa adherents, and on Bsod-nams-rgya-mtsho's death they acquired a proprietary interest in the order and some claims on Tibet itself when the fourth Dalai Lama was conveniently discovered in the Tümed royal family.

To support their protégé the Mongols sent armed bands into Tibet. Their opponents were the Red Hat Lama, head of a Karma-pa subsect, and his patron the Gtsang king. That phase of rivalry ended inconclusively with the early death of the fourth Dalai Lama and the decline of Tümed Mongol authority in Mongolia. The next came when Güüshi Khan, leader of the Khoshut tribe, which had displaced the Tümed, appeared as champion of the Dge-lugs-pa. In 1640 he invaded Tibet, defeating the Gtsang king and his Karma-pa supporters.

In 1642 with exemplary devotion, Güüshi enthroned the Dalai Lama as ruler of Tibet, appointing Bsod-nams chos-'phel as minister for administrative affairs and himself taking the title of king and the role of military protector. These three forceful personalities methodically and efficiently consolidated the religious and temporal authority of the Dge-lugs-pa. Lhasa, long the spiritual heart of Tibet, now became the political capital as well. Dge-lugs-pa supremacy was imposed on all other orders, with special severity toward the Karma-pa. A reorganized district administration reduced the power of the lay nobility.
The grandeur and prestige of the regime were enhanced by reviving ceremonies attributed to the religious kings, by enlarging the nearby monasteries of 'Bras-spungs, Sera, and Dga'-Idan, and by building the superb Potala palace, completed by another great figure, Sangs-rgyas rgya-mtsho, who in 1679 succeeded as minister regent just before the death of his patron the fifth Dalai Lama. By then a soundly based and unified government had been established over a wider extent than any for eight centuries.

The installations of the fifth Dalai Lama at Lhasa (1642) and the Ch'ing, or Manchu, dynasty in China (1644) were almost synchronous. Good relations with Tibet were important to the Manchu because of the Dalai Lama's prestige among the Mongols, from whom a new threat was taking shape in the ambitions of the powerful Oyrat of western Mongolia.

Elsewhere Lhasa's expanding authority brought disagreements with Bhutan, which held its own against Tibetan incursions in 1646 and 1657, and with Ladakh, where a campaign ended in 1684 in Tibetan withdrawal to an accepted frontier when the Ladakhi king appealed for help to the Muslim governor of Kashmir.

The Dalai Lama's death in 1682 and the discovery of his five-year-old reincarnation in 1688 were concealed by Sangs-rgyas rgya-mtsho, who was intent on continuing the administration without disturbance. He informed the Manchu only in 1696. Emperor K'ang-hsi (reigned 1661-1722) was incensed at the deception. In 1703 he discovered an ally in Tibet and an antagonist to Sangs-rgyas rgya-mtsho when Lha-bzang Khan, fourth successor of Güüshi, sought to assert rights as king that had atrophied under his immediate predecessors.

The behaviour of the sixth Dalai Lama, Tshangs-dbyangs-rgya-mtsho, who preferred poetry and libertine amusements to religion, gave Lha-bzang his opportunity. In 1705 with the Emperor's approval, he attacked and killed Sangs-rgyas rgya-mtsho and deposed Tshangs-dbyangs-rgya-mtsho as a spurious reincarnation. The Tibetans angrily rejected him and soon recognized in east Tibet the infant reincarnation of the dead Tshangs-dbyangs-rgya-mtsho.

In 1717 the Oyrat, nominally Dge-lugs-pa supporters, took advantage of Tibetan discontents to intervene in a sudden raid, defeating and killing Lha-bzang. Fear of hostile Mongol domination of Tibet compelled the Emperor to send troops against the Oyrat. After an initial reverse, his armies drove them out in 1720 and were welcomed at Lhasa as deliverers, all the more because they brought with them the new Dalai Lama, Bskal-bzang-rgya-mtsho. For the next 200 years there was no fighting between Tibetans and Chinese; but after evicting the Oyrat the Emperor decided to safeguard Manchu interests by appointing representatives--generally known as Ambans--at Lhasa, with a small garrison in support.

The Tibetans, interpreting this as another patron-priest relationship, accepted the situation, which, generally left them to manage their own affairs. It was only in recurring crises that Manchu participation became, briefly, energetic. Imperial troops quelled a civil war in Tibet in 1728, restored order after the political leader was assassinated in 1750, and drove out the Gurkhas, who had invaded from Nepal in 1792. As Manchu energy declined, the Tibetans became increasingly independent, though still recognizing the formal suzerainty of the emperor, behind which it sometimes suited them to shelter. At no time did the Ambans have administrative power, and after 1792, when Tibet was involved in wars with Ladakh (1842) and Nepal (1858), the Manchu were unable to help or protect them.

No Dalai Lama until the 13th approached the personal authority of the "Great Fifth." The seventh incarnation was overshadowed by Pho-lha, a lay nobleman appointed ruler by the Manchu; the eighth was diffident and retiring. But after the Pho-lha family's regime, Dge-lugs-pa churchmen resumed power and held onto it through a series of monk regents for about 145 years.

Chinese contacts affected Tibetan culture less than might be expected. They helped to shape the administrative machinery, army, and mail service, which were based on existing institutions and run by Tibetans. Chinese customs influenced dress, food, and manners; china and chopsticks were widely used by the upper classes. The arts of painting, wood carving, and casting figures continued on traditional lines, with much technical skill but few signs of innovation. An important effect of Manchu supremacy was the exclusion of foreigners after 1792. That ended the hopes of Christian missionaries and the diplomatic visits from British India, which had been started in 1774. Tibet was now closed, and mutual ignorance enshrouded future exchanges with its British neighbours in India.