During the 19th century, Britain and the Russian Empire vied to fill the power vacuums that had been left by the declining Ottoman Empire, Qajar dynasty and Qing Dynasty. This rivalry in Eurasia came to be known as the "Great Game". As far as Britain was concerned, defeats inflicted by Russia on Persia and Turkey demonstrated its imperial ambitions and capabilities and stoked fears in Britain of an overland invasion of India. In 1839, Britain moved to pre-empt this by invading Afghanistan, but the First Anglo-Afghan War was a disaster for Britain.
Russian victories against which countries increased British fears?
Persia and Turkey