The Bangladesh Liberation War , as it is now known, escalated as India and Pakistan formally acknowledged the "existence of a state of war between the two countries", even though neither government had formally issued a declaration of war .  As the situation in his home district of East Pakistan worsened, Amin was appointed Prime Minister by President General Yahya Khan on 6 December 1971. On 20 December 1971, however, Yahya Khan resigned, leaving the Deputy Prime Minister (and Foreign Minister) Zulfikar Ali Bhutto to be sworn in as the new President. Two days later, Amin was appointed as Vice President of Pakistan, the only person to have held this post. He continued to hold this post until martial law was lifted on 21 April 1972.