It refers to a plan drawn up by the Pakistan Army in May 1965, that consisted of an attack on the vital Akhnoor Bridge in Jammu and Kashmir, India.

The operation saw initial success, but was aborted when the Indian Army opened a new front in the Pakistani province of Punjab in order to relieve pressure in Kashmir.

This forced Pakistan to abandon Grand Slam and fight in Punjab, so that the operation ended in failure and stated objectives were not achieved.

[16] At the time of the opening attack of Operation Grand Slam, the Chhamb Jaurian sector was defended on the Indian side by the 191st (Independent) Infantry Brigade, comprising three battalions, and supported by a squadron of 20 Lancers, which was equipped with AMX-13 light tanks.

The plan was to infiltrate thousands of troops into Jammu and Kashmir, India in the guise of 'mujahideen', who would carry out sabotage to demoralise the Indian forces and incite the local population to revolt.

[19] In addition, the Indian Army moved across the cease-fire line to cut off the Pakistani infiltration routes and captured the Haji Pir pass in Azad Kashmir and some heights in the Kargil sector.

[20] On 24 August, General Akhtar Malik started pressing the Army Headquarters for permission to launch the Operation Grand Slam.

In his view, unless it was launched, it was only a matter of time before all the Gibraltar forces in Jammu and Kashmir, India would be captured or killed, and nothing would have been achieved from the whole operation.

Bhutto is cited by the Army officers as having been the main driving force behind the entire military operation, and he was also said to be close enough to Ayub Khan to obtain his approval.

When the attack recommenced on 3 September, the Indian forces in the sector were sufficiently reinforced to hold out for a few more days, but they did not have the strength to launch a counterattack.

As the attack carried on for two more days without any significant gains in territory, the Indian Army opened up a new front, on 6 September, across the sensitive state of Punjab in Pakistan.

Realising the gravity of the threat, the Pakistani Army stopped its thrust into Kashmir and diverted forces to counter the Indian incursion.