Why did India fight?
Because the Indians wanted India to be ruled by Indians.
When did India fight Russia? India was a Crown Colony (British Colony) from the 1800s up thru WWII (1945). And Russia disappeared in 1918 (officially on or about 1922) and became the USSR...until 1990. From about 1990 Russia has been Russia (NOT the USSR). So...did India fight Russia in 1990...or when?