Nicholas's successor Alexander II (1855–81) enacted significant changes throughout the country, including the emancipation reform of 1861. These reforms spurred industrialisation, and modernized the Imperial Russian Army, which liberated much of the Balkans from Ottoman rule in the aftermath of the 1877–78 Russo-Turkish War. During most of the 19th and early 20th century, Russia and Britain vied to fill the power vacuums that had been left by the declining Ottoman Empire, Qajar Iran, and the Qing dynasty. This rivalry between the two major European empires came to be known as "The Great Game".