After Pakistan's surrender late in 1971, people in Bangladesh rejoiced at their liberation. This was followed by a need to get international acceptance for Bangladesh, as only a few countries recognised the new nation. Bangladesh sought admission in the UN with most voting in its favour, but China vetoed this as Pakistan was its key ally. However the United States grudgingly recognized it, and to ensure a smooth transition, in 1972 the Shimla Agreement was signed between India and Pakistan. The treaty was a watershed in the history of the South Asian region as it ensured that Bangladesh would get official recognition from Pakistan and its principal allies in exchange for the return of the Pakistani PoWs. India treated all the PoWs in strict accordance with the Geneva Convention, rule 1925. It released more than 90,000 Pakistani PoWs in a record five months. As a gesture of goodwill, the nearly 200 soldiers who were sought for war crimes by Bengalis were also pardoned by India. The accord also gave back more than 13,000 km² of land that Indian troops had won in West Pakistan during the war, holding on to a few strategic places; most notably Kargil (which would in turn again be the focal point for a war between the two nations in 1999). This was done as a measure of ensuring "lasting peace" and was acknowledged by many observers as a sign of maturity by India. But some in India felt that the treaty had been too lenient to Bhutto, who had pleaded for more leeway as he felt that the fragile democracy in Pakistan would crumble if the accord was perceived as being too harsh in Pakistan.
http://en.wikipedia.org/wiki/Bangladesh_Liberation_War#End_of_the_war