The Uriankhai Republic was the name of a short-lived Russian-sponsored state in Central Asia.
The Republic was roughly contiguous with the modern Russian republic of Tannu-Tuva, and lasted from its proclamation in 1912 until it was taken over by Bolshevik forces in 1919. The Bolsheviks briefly took over the reins of power, and from 1919-1921 the state was known as the Tannu People's Republic.
Before 1912, the territory which became the Uriankhai Republic was known as Tannu Uriankhai and was part of Qing Mongolia. Under the terms of an 1860 agreement between the Qing rulers of China (which at the time included both Inner and Outer Mongolia) and the Russians, limited Russian settlement was permitted, but the territory remained under Qing rule.
1911 saw numerous uprisings and unrest in China itself, and in this context, Tsar Nicholas II of Russia sponsored a secessionist uprising on the part of the Turkic Tuvan majority. Aided by both Russian settlers within the territory and Tsarist forces sent in from Russian Siberia, the Tuvans seceded from China, and the following year proclaimed the establishment of the Uriankhai Republic under Russian protection.
Russia immediately recognised the state, as did several other nations, notably Persia and Japan, but China refused to give official recognition to the secessionist state. From 1912 to 1921, the Qing rulers of China continued to refer to the state as a "rebel province".
In 1919, during the Russian Civil War, Bolshevik Communist forces overran the Russian-sponsored Republic and instituted a communist regime. The Tannu People's Republic, however, was short-lived, and in 1921 White Russian forces pushed the Communists out of the Republic and back to the Soviet Socialist Republic of Siberia.
This time, the Russian White forces annexed the country outright. This annexation was supposedly at the request of a group of prominent Tuvan citizens, including High Lama Byyat Lopsang and Bishop Ondar-ool Orjaq of Chadan, though many historians believe that this "request" was coerced by the Russian forces.
At any rate, the state became formally a part of the Russian Empire in 1921.