The 4th Battalion of the Sri Lanka Sinha Regiment was raised on 1stDecember 1985 at Ambepussa. The initial strength of the Battalion was 18 officers and 405 other rankers. Lieutenant Colonel HS Hapuarachchi was appointed as the first Commanding Officer of the Battalion.
The majority of troops for the Battalion were those who previously were from the 1st Battalion of the Sinha Regiment while 300 others were those newly recruited to the Army.
On 3rd March 1986, the Battalion took over duties in Seruwila, Serunuwara and Dehiwatta in the Eastern Province where they performed their duties up to 12thApril 1986. On 25thDecember 1986 troops of the Battalion engaged captured terrorist camps in Verugalaru, Trincomalee.
Major General Denzil Kobbekaduwa, Brigadier Wijaya Wimalaratne and Lieutenant Colonel Susantha Mendis engaged in a conversation while on the field
Commencing 6th May 1986 the Battalion moved to the North by land air and sea routes and was deployed in Elephant Pass, Jaffna Fort and Nawatkuli.
On 6th June 1986 while performing duties in the North, S/31845 Lance Corporal Somathilaka BS was killed. This was the first instance of a death of a ranker of the Battalion at the hand of the separatist terrorists.
On 28th July 1986 the LTTE attacked the Jaffna Fort concentrating on the Officers' Mess as a result of which the Commanding Officer along with the Adjutant, Captain LWCBB Rajaguru were seriously wounded while Captain UJ Wickramanayaka was killed, thus, recording the first death of an officer of the Battalion at the hands of the separatist terrorists.
Troops taking a break at Elephant Pass Camp
On 5th November 1986 troops of the HQ troops stationed at Ambepussa were deployed to a newly established camp at Singhawilluwaththa in Puttalam. On 10th December 1986 the 'C'company troops relieved from Elephant Pass Camp were redeployed at Kankesanthurai commonly known as KKS.
On 28th December 1986, at the time the 'A' company was stationed at the Jaffna Fort it came under an attack by the LTTE who succeeded in taking over its control. On 23rd March 1987 the LTTE attacked the telecommunication building and police quarters complex in Panney as a result of which 5 soldiers of the Battalion were killed and another 5 soldiers reported as'missing in action'. Subsequent to this incident the excluding the 'A'company all other companies were relieved from operational duty in the North and returned to their camp in Puttalam.
On 16th April 1987 troops of the Battalion were deployed to track down the LTTE cadres who attacked a passenger bus transporting civilians in Kithulutuwa in the East following which the troops remained stationed at a number of camps in Trincomalee.
