The dramatic change in the Indian Navy's capabilities and stance was emphatically demonstrated during the Indo-Pakistani War of 1971. Under the command of Admiral Sardarilal Mathradas Nanda, the navy successfully enforced a naval blockade of West and East Pakistan. Pakistan's lone long-range submarine was sunk following an attack by the destroyer off the coast of Visakhapatnam in the midnight of 3–4 December 1971. On 4 December, the Indian Navy successfully executed Operation Trident, a devastating attack on the Pakistan Naval Headquarters of Karachi that sank a minesweeper, a destroyer and an ammunition supply ship. The attack also irreparably damaged another destroyer and oil storage tanks at the Karachi port. To commemorate this, 4 December is celebrated as the Navy Day. This was followed by Operation Python on 8 December 1971, further deprecating the Pakistan Navy's capabilities. Indian frigate , commanded by Captain M. N. Mulla was sunk by , while was damaged on the west coast. In the Bay of Bengal, the aircraft carrier was deployed to successfully enforce the naval blockade on East Pakistan. Sea Hawk and the Alizé aircraft from INS "Vikrant" sank numerous gunboats and Pakistani merchant marine ships. To demonstrate its solidarity as an ally of Pakistan, the United States sent Task Force 74 centred around the aircraft carrier into the Bay of Bengal. In retaliation, Soviet Navy submarines trailed the American task force, which moved away from the Indian Ocean towards Southeast Asia to avert a confrontation. In the end, the Indian naval blockade of Pakistan choked off the supply of reinforcements to the Pakistani forces, which proved to be decisive in the overwhelming defeat of Pakistan.