Answer:
Before the British left India there was widespread violence between the Hindus and the Muslims which were the two main religions of India. This led to the British dividing India between Pakistan (East and West) and India. Pakistan was to be a Muslim country and India was to be overwhelming Hindu.
1. Refugee Crisis.
The division created a massive refugee crisis and Hindus in Pakistan tried to cross back to India and Muslims in India tried to cross to Pakistan. Millions of people were displaced as they tried to move and it took some time before they were resettled in their new countries.
2. Violence.
As the people moved, large scale violence was committed by both sides as they took advantage of the chaos. Hindu extremists were more extreme however and engaged in ethnic cleaning of Muslims in many areas to ensure that they moved out of India. It is estimated that hundreds of thousands died during this time.
3. Generational animosity between India and Pakistan.
As a result of the violence that accompanied the split, India and Pakistan have not trusted each other since then and have engaged in conflict a number of times as a result. Even today the two countries are not on friendly terms.