It has been a nation separate from India only since the early 1930's.
Maybe the Brits thought that separating the Muslim population from the Hindu population would prevent civil war?
So now we're on the brink of a nuclear exchange - that's some alternative outcome....
The British had nothing to do with the partition. Once they started to withdrawal, the Muslims and Hindus started attacking each other. Muslims did not trust the Congress Party, which had a lock on the post independence government. Over 2,000,000 people died before the British negotiated a partition agreement to slow the killing.
They have since fought several wars. The most recent was the Kargill War in 1999.