Ground operations

Before the start of the war, the Indian Army was well organised on both fronts and enjoyed significant numerical superiority over the Pakistan Army.The Indian Army's extraordinary war performance at both fronts restored the prestige, confidence, and dignity that it had lost during the Sino-Indian War in 1962.

When the conflict started, the war immediately took a decisive turn in favour of India and their Bengali rebel allies militarily and diplomatically. On both fronts, Pakistan launched several ground offensives, but the Indian Army held its ground and initiated well-coordinated ground operations on both fronts. Major ground attacks were concentrated on the western border by the Pakistan Army, fighting together with the Pakistan Marines in the southern border, but the Indian Army was successful in penetrating into Pakistani soil. It eventually made some quick and initial gains, including the capture of around 15,010 km² (5,795 sq mi) of Pakistani territory; this land gained by India in Azad Kashmir, Punjab and Sindh sectors was later ceded in the Simla Agreement of 1972, as a gesture of goodwill Casualties inflicted to Pakistan Army's I Corps, II Corps, and Pakistan Marines' Punjab detachment were very high, and many soldiers and marines perished due to lack of operational planning and lack of coordination within the marine-army formations against Indian Army's Southern and Western Commands. By the time the war came to end, the army soldiers and marines were highly demoralised– both emotionally and psychologically– on the western front and had no will to put up a defensive fight against the approaching Indian Army soldiers.

The War Enquiry Commission later exposed the fact that for the Pakistan Army and Pakistan Marines, the arms and training of marines, soldiers and officers were needed at every level, and every level of command.

On 23 November 1971, the Indian Army conventionally penetrated to the eastern fronts and crossed East Pakistan's borders to join their Bengali nationalist allies. Contrary to the 1965 war, which had emphasised set-piece battles and slow advances, this time the strategy adopted was a swift, three-pronged assault of nine infantry divisions with attached armoured units and close air support that rapidly converged on Dacca, the capital of East Pakistan. Lieutenant General Jagjit Singh Aurora, the General Officer Commanding-in-Chief of the Indian Army's Eastern Command, led the full Indian thrust into East Pakistan. As the Indian Eastern Command attacked the Pakistan Eastern Command, the Indian Air Force rapidly destroyed the small air contingent in East Pakistan and put the Dacca airfield out of commission. In the meantime, the Indian Navy effectively blockaded East Pakistan.

The Indian campaign's "blitzkrieg" techniques exploited weaknesses in the Pakistani positions and bypassed opposition; this resulted in a swift victory. Faced with insurmountable losses, the Pakistani military capitulated in less than a fortnight and psychological panic spread in the Eastern Command's military leadership. Subsequently, the Indian Army encircled Dacca and issued an ultimatum to surrender in "30-minutes" time window on 16 December 1971. Upon hearing the ultimatum, the East-Pakistan government collapsed when the Lt-Gen. A.A.K. Niazi (Cdr. of Eastern Command) and his deputy, V-Adm. M.S. Khan, surrendered without offering any resistance. On 16 December 1971, Pakistan ultimately called for unilateral ceasefire and surrendered its entire four-tier military to the Indian Army– hence ending the Indo-Pakistani war of 1971.

On the ground, Pakistan suffered the most, with 8,000 killed and 25,000 wounded, while India only had 3,000 dead and 12,000 wounded. The loss of armoured vehicles was similarly imbalanced and this finally represented a major defeat for Pakistan.