Indian troops breached the international boundary into Pakistan close to Lahore in the early hours of September 6, 1965. The majority of the conflict between India and Pakistan had up until that point been limited to Jammu and Kashmir. India virtually immediately altered the nature of the fight by sending troops over the border.
The move was not a sudden escalation. It was a response to a situation that had been building for weeks. Pakistani forces had already launched infiltration operations in Kashmir and then followed them with a conventional offensive aimed at cutting India’s supply lines. Indian leaders decided that the only way to break that pressure was to widen the battlefield.
The offensive that began that morning is usually referred to as Operation Riddle.
How the conflict began
The story starts in August 1965, when Pakistan launched Operation Gibraltar. Thousands of armed infiltrators crossed the ceasefire line into Jammu and Kashmir. Many were regular Pakistani soldiers operating in civilian clothing.
The intention was to incite discontent within Kashmir and promote a rebellion against Indian governance. The political climate in the area, according to Pakistan's government, would encourage such an uprising.
However, it was not how events transpired. Locals in a number of locations alerted Indian authorities to unusual activity and strange armed individuals. To find the infiltrators, Indian troops started combing operations.
At the same time, the Indian Army pushed back across some parts of the ceasefire line. One of the most important outcomes was the capture of the Haji Pir Pass in late August. The pass was a key route used for infiltration into the Kashmir Valley.
For Pakistan, losing that route was a serious setback.
Pakistan opens a larger offensive
Pakistan responded with a much larger military move. On 1 September 1965 it launched Operation Grand Slam in the Chhamb–Jaurian sector of Jammu.
The target was Akhnoor, a town that served as a vital road link supplying Indian forces deployed deeper in Kashmir. If Pakistan captured it, Indian troops in the region could have faced serious logistical problems.
The Pakistani attack initially made progress and created concern within Indian military circles. Tanks and artillery pushed forward and Indian positions in the sector came under pressure.
Indian commanders began looking for a way to relieve that pressure quickly.
A different idea takes shape
Instead of continuing to fight only in Kashmir, Indian military planners proposed something more dramatic: open a new front along the international border in Punjab.
The reasoning was straightforward. If Indian troops threatened Lahore and other Pakistani cities close to the border, Pakistan would have to shift troops away from Kashmir to defend them.
Crossing the international border would turn the conflict into a full-scale war, so the decision ultimately rested with Prime Minister Lal Bahadur Shastri. After consultations with the army leadership, he approved the plan.
The goal was not to capture large parts of Pakistani territory. The aim was to force Pakistan to fight on multiple fronts.
The advance toward Lahore
Before dawn on 6 September, Indian formations moved across the border at several points. Troops advanced toward Lahore while others moved in the direction of Kasur.
The move surprised Pakistani commanders. Indian units pushed forward rapidly and soon reached the Ichhogil Canal, a major defensive barrier protecting Lahore.
In some sectors Indian troops crossed the canal and began fighting close to the outskirts of the city. For Pakistan’s leadership, the development was alarming. Lahore was suddenly within reach of the battlefield.
The move had the effect Indian planners hoped for. Pakistani forces began shifting troops and armour from the Kashmir sector to reinforce the Punjab front.
The war spreads across Punjab
Once the new front opened, the fighting spread quickly across the plains.
In the Lahore sector, Indian troops captured several positions and fought heavy engagements around Burki and Dograi. These battles were intense and often fought at close range as both sides tried to hold strategic ground.
Further south, the conflict produced one of the best-known battles of the war. Pakistani forces launched a large armoured attack toward Khem Karan using Patton tanks supplied by the United States.
Indian troops halted the advance near the village of Asal Uttar. Dozens of Pakistani tanks were destroyed in the fighting, leaving the battlefield scattered with wrecked armour. Soldiers later began referring to the area as the “graveyard of Patton tanks”.
At the same time, another major front developed further north near Sialkot. Both armies deployed large tank formations there, leading to battles around Phillora and Chawinda. Hundreds of tanks were involved in these engagements, making them some of the largest armoured clashes since the Second World War.
Air forces join the fighting
As the ground battles intensified, both countries brought their air forces into action.
The Indian Air Force carried out strikes against Pakistani air bases and military installations, including the important base at Sargodha. Pakistan’s air force responded with attacks on Indian airfields and troop positions.
The conflict was no longer confined to the ground. Aircraft from both sides now played an important role in supporting operations.
Naval activity remained limited. Pakistan carried out a bombardment of the coastal town of Dwarka, mainly as a show of force.
The fighting slows
By mid-September the war had become a costly stalemate. Both armies had suffered significant losses in men and equipment. Tanks had been destroyed in large numbers and artillery exchanges were constant.
Despite fierce fighting, neither side managed to achieve a decisive breakthrough.
International pressure for a ceasefire began to grow. Both the United States and the Soviet Union were concerned that the conflict could expand further during the Cold War.
On 23 September 1965, India and Pakistan agreed to a ceasefire under United Nations supervision.
Why Operation Riddle mattered
Although the ceasefire restored most of the earlier positions, the decision to cross the international border had already changed the war.
By opening the Punjab front, India forced Pakistan to divide its military effort. Pakistani forces that had been pressing hard in Kashmir had to be redeployed to defend Lahore and other areas.
The war formally ended with the Tashkent Agreement in January 1966, when both sides agreed to withdraw to their pre-war positions.
Looking back, Operation Riddle stands out as one of the turning points of the conflict. What began as infiltration and local fighting in Kashmir quickly turned into a full-scale war across Punjab once India decided to take the battle across the border.
The events of 6 September showed how quickly the course of a war can change when the battlefield itself expands.
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