1. India had lost a war against China in 1962
2. Pandit Nehru had died in 1964
3. Pakistan saw this as an opportune moment to strike against India
This battle is of significance largely due to the fact that it was the battle which turned the tide of the 1965 war towards India. Until this point, Pakistan had made significant territorial gains. However it was with this battle, one involving some amazing tactical moves on part of India, that boosted the morale of the Armed Forces to such an extent that by the time the ceasefire was implemented, Indian forces had reached Lahore.
Some important points to note are:
1. Pakistan in 1965 had a superior artillery as compared to India
2. Pakistan was at it's strongest in terms of military preparation and countrywide stability
3. India was still recovering from the military loss to China and the loss of one of it's greatest leader post Independence and a Prime Minister of 14 years
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The Battle of Asal Uttar (also called the Battle of Khemkaran in some sources) was of particular interest to students of armored combat. This battle was the largest tank on tank combat in the generational period between World War Two and the Arab-Israeli Six Day War.
On September 10, 1965 three Indian armored regiments with 45 old American M4 Sherman tanks, 45 light French built AMX-13 tanks, and 45 British-built Centurion tanks were arrayed outside the village of Asal Uttar in the western Punjab province of India. These tanks had set up defensive positions in a "U" formation and were superbly camouflaged by tall un-harvested sugarcane stalks. The Indian force was assembled to attempt to stop the invading Pakistani armored drive. The Pakistani force contained no less than 300 of the new American M47 Patton tanks along with a few M24 Chaffee Tanks. The 46-ton Patton was considered one of the best and most modern designs of the time and included a 90mm main gun that outranged the Indian tanks. The Indian tanks were largely outgunned (the Shermans and AMX-13s only having 75mm main guns) as well as grossly outnumbered by a factor of no less than 2:1. Four inches (100mm) of steel armor plating on the Patton's made them proof to all but the most close range or lucky shots
Advancing into an Indian artillery barrage, the Pakistani armor fell into the Indian trap. Much like the Americans at the Battle of Bunker Hill the Indian gunners held fast until they could 'see the whites of their enemy's eyes". Opening fire from their camouflaged hiding places at ranges of as short as five hundred meters the smaller Indian tanks were able to penetrate the Pakistani Pattons from all angles and shortly set dozens on fire. The Pakistanis left the field in disarray, leaving almost a hundred tanks behind. The Indians lost 32 tanks but gained a powerful victory, which led to a stalemate and a ceasefire that ended the 1965 Indo-Pakistan War on September 22nd.
Another tactical victory was luring the Pakistani tanks into areas with soft soil which completely ruled out a quick retreat for their tanks.
The battle also witnessed the personal bravery of an Indian soldier Abdul Hamid being honoured with the Param Vir Chakra, India's highest military award, for having knocked out seven enemy tanks with a recoil-less gun.
Participating in the battle was a young Lt. Pervez Musharraf, in the Pakistani 1st Armored Division. He later became the president of the Pakistani state. Today the site of the battle is referred to as Patton Nagar (Patton City) after the large number of Patton tanks captured there.
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Sources:
http://modern-war.suite101.com/article.cfm/battle_of_asal_uttar_1965