1971 Bangladesh atrocities
In 1947, the United Kingdom split British India into two countries: India and Pakistan.  The idea was that Hindus would live in India and Muslims would live in Pakistan.  But it was not so simple.  Because Hindus and Muslims lived in so many different places, East Pakistan and West Pakistan were about 1000 miles apart, with all of India in between them.  Also, not all Muslims are the same.  The East Pakistanis and West Pakistanis did not speak the same language and did not always like each other.