The 6thBattalion of the Sri Lanka Sinha Regiment was formed on 10th August 1987. The initial strength of the Battalion was 17 officers and 552 other ranks who had been released from the 1st & 4th Sinha Regiments.
Lieutenant Colonel AG Weerasekara was appointed as the Commanding Officer.
The Headquarters of the Battalion having being established at the Konduvattuvan Camp in Ampara, the rifle companies were deployed in the Digamadulla District tasked with securing the villages in the district.
The Battalion worked closely with the Indian Peace Keeping Force (IPKF) deployed in Digamadulla in providing protection to the villages.
On 8th June 1988 a mobile patrol in the Buddangala area was attacked by the separatists resulting in the death of S/32432 Lance Corporal Karunarathne PDA, thus recording the first soldier of the battalion to be killed in action.
On 20th September 1988, Major HR Stephen took over The Command of the Battalion.
The Battalion was called out to carryout counter insurgency tasks against the activity of the JVP insurgents which the Battalion executed successfully. On 26th April 1989 the Battalion moved to the Hambanthota district where the JVPs activities had intensified. In its efforts to maintain law & order the Battalion lost (killed) 23 soldiers.
On 10th April 1990 the Battalion returned to Ambepussa and underwent Battalion Training before being deployed to the North.
Having arrived in the North on 26th May 1990 the Battalion established its headquarters at Vasavilan. The companies were deployed at Kankasanthurai, Kilinochchi, Jaffna Fort, Vasavilan and Elephant Pass. At the time, the Battalion was the only infantry battalion of the Regular Army that to have been deployed in the North.
On 11th June 1990, the separatist terrorists launched attacks on the Army positions in the North, this commencing what is referred to as Eelam War II.
