History of modern Mongolia
In 1924, the constitutional monarchy was no longer used when the king died. The Mongolian People's Republic was formed. The name of the capital city was changed from Küriye to Ulan Bator. It was ruled by the Mongolian People's Revolutionary Party and had very close relationship with the Soviet Union. The country was socialist.
The Republic of China had Sino-Soviet Treaty of Friendship and Alliance with the USSR. However, the Soviet Union was later criticised for helping the People's Republic of China in the Chinese Civil War. In United Nations General Assembly Resolution 505, the Republic of China claimed that they would not give up Mongolia as a part of China.
In February 1992, Mongolia gave up socialism. The name of the country was shortened to "Mongolia".