evidence: Although Mongol-led confederations sometimes exercised wide political power over their conquered territories, their strength declined rapidly after the Mongol dynasty in China was overthrown in 1368. The Manchus, a tribal group which conquered China in 1644 and formed the Qing dynasty, were able to bring Mongolia under Manchu control in 1691 as Outer Mongolia when the Khalkha Mongol nobles swore an oath of allegiance to the Manchu emperor. The Mongol rulers of Outer Mongolia enjoyed considerable autonomy under the Manchus, and all Chinese claims to Outer Mongolia following the establishment of the republic have rested on this oath. In 1727, Russia and Manchu China concluded the Treaty of Khiakta, delimiting the border between China and Mongolia that exists in large part today. Outer Mongolia was a Chinese province (1691-1911), an autonomous state under Russian protection (1912-19), and again a Chinese province (1919-21). As Manchu authority in China waned, and as Russia and Japan confronted each other, Russia gave arms and diplomatic support to nationalists among the Mongol religious leaders and nobles. The Mongols accepted Russian aid and proclaimed their independence of Chinese rule in 1911, shortly after a successful Chinese revolt against the Manchus. By agreements signed in 1913 and 1915, the Russian Government forced the new Chinese Republican Government to accept Mongolian autonomy under continued Chinese control, presumably to discourage other foreign powers from approaching a newly independent Mongolian state that might seek support from as many foreign sources as possible.