Original: During the collapse of the Qing Dynasty in 1911 , Mongolia declared independence , but had to struggle until 1921 to firmly establish de facto independence from the Republic of China , and until 1945 to gain international recognition .
Simplified: During the collapse of the Qing Dynasty in 1911 , Mongolia declared independence , but had to struggle with the Soviet Union 's help , until 1921 before the world accepted its independence .