Under the provisions of the Indo-Sri Lankan Accord, an Indian military contingent was dispatched to northern Sri Lanka. This contingent, named the Indian Peacekeeping Force was composed of army and paramilitary units from the Indian Army's Southern Command, headquartered in Madras. The IPKF, when it was initially dispatched to Sri Lanka, numbered about 1,600 personnel. As the cease-fire failed to take hold, and as the tenacity of the Tamil insurgents became increasingly evident, the force was steadily augmented. Within three months of its deployment, the IPKF presence in Sri Lanka had grown to 20,000 personnel. At the end of the year, two brigades of Muslim troops were introduced into Eastern Province to deal with growing tension in the Islamic community of that area. By January 1988, the overall force had a total strength of 50,000 personnel from three Indian Army divisions, plus supporting units. The following month it was announced in the Indian Parliament that the IPKF would be increased to 70,000 personnel organized tactically into fifteen brigades. Some Sri Lankan sources said privately that the force had grown well in excess of this total, possibly surpassing 100,000 troops, and that its presence in Sri Lanka might well exceed the duration of the insurgency. In mid-1988, however, the Indian government did withdraw from Sri Lanka some of its more heavily armed artillery and armored units that were obviously unsuitable for fighting a counterinsurgency war.

At the time of its deployment, the IPKF was intended as a truce supervisory force that would oversee the disarming of the Tamil insurgents and the disengagement of the Sri Lankan government forces. As the cease-fire between the two sides broke down, however, the Indians were compelled to assume a combat role and were sent into action against the Tamil guerrillas overrunning the Jaffna Peninsula. In this operation, codenamed Operation Parwan, IPKF units of the 54th Indian Army division launched a five-pronged attack to clear the area of insurgents. After sixteen days of fighting, Jaffna fell to the Indians, and the Tamil combatants retreated to the more inaccessible areas of Northern and Eastern provinces.

Among the residents of Jaffna, the assault on the city provoked widespread bitterness toward the Indian troops, as reports spread of atrocities and high civilian casualties caused by careless bombardment of populated areas. Many of these reports were believed to be the result of Tamil insurgent propaganda. Nonetheless, in early 1988 the Indian Army acknowledged that there had been serious disciplinary problems during the campaign, and a number of soldiers were sent back to India after conviction on rape charges. Such gestures also hinted that the IPKF seemed disposed to apply the lessons learned from the Jaffna offensive and to abandon its previous hamfisted tactics and insensitivity to the civilian population. When continued insurgent activity required redeployment of IPKF units to Eastern Province and the inland districts of Northern Province, the Indian forces embarked on an aggressive civic action progr2de gram to restore the infrastructure in war-ravaged areas, and on an intensive campaign of heavy patrolling to keep the guerrillas off balance. The Indians gained experience in both urban and counterinsurgency warfare and made some progress in keeping the Tamil insurgents at bay. However, the guerrillas were proving a more intractable foe than anticipated, and observers were not optimistic about an early conclusion to the conflict.

Data as of October 1988