Pakistan, since independence, was geo-politically divided into two major regions, West Pakistan and East Pakistan. East Pakistan was occupied mostly by Bengali people. After a Pakistani military operation and a genocide on Bengalis in December 1971, following a political crisis in East Pakistan, the situation soon spiralled out of control in East Pakistan and India intervened in favour of the rebelling Bengali populace. The conflict, a brief but bloody war, resulted in the independence of East Pakistan. In the war, the Indian Army invaded East Pakistan from three sides, while the Indian Navy used the aircraft carrier INS Vikrant (R11) to impose a naval blockade of East Pakistan. The war saw the first offensive operations undertaken by the Indian Navy against an enemy port, when Karachi harbour was attacked twice during Operation Trident (1971) and Operation Python. These attacks destroyed a significant portion of Pakistan's naval strength, whereas no Indian ship was lost. The Indian Navy did, however, lose a single ship, when INS Khukri (F149) was torpedoed by a Pakistani submarine. 13 days after the invasion of East Pakistan, 93,000 Pakistani military personnel surrendered to the Indian Army and the Mukti Bahini. After the surrender of Pakistani forces, East Pakistan became the independent nation of Bangladesh.