By 15th June 1990 the Battalion engaged in 'Operation Clean-Up' to retake Bakki Ela and Kalawanchkudi from the clutches of the terrorist. This operation took place in the areas such as Wellaweli, Bakki Ela, Kalawanchikudi, Periyaporathivu. On successful completion of the operation the troops were given a break to rest at the Kondawatuwana Camp in Ampara. Although there was no major battle taking place at the time, operations that were of minor scale major were launched by troops in the areas of Samanthurai, Kalmunai and Akkaraipattu. The Headquarters of the Battalion and the 'D' Company were re-located to Kerativu Camp while the 'A' Company remained at Akkaraipattu.
In the same year, the Battalion took part in 'Operation Thrividabalaya' and the Battalion was took total control of the Mandaitivu Island. The number of terrorists killed stood around 80 while a large stock of arms and ammunition was taken into custody. The own casualty figures remained at two other ranks killed and 25 wounded. On 13th September 1990 the Battalion linked up with other infantry battalions in the joint undertaking of 'Operation Thrivida Balaya II' launched with the aim of rescuing a total 172 Army and Police personnel; 2 officers, 51 soldiers, an ASP, 6 police sub inspectors and 112 police constables, under siege at the Jaffna Fort.
Following the successful completion of the operation, the Battalion was deployed to Konduwatuwana, Bakmitiyawa and Malwatta areas in Ampara.
On 1st December 1990 Major P Pannipitiya was appointed as the Commanding Officer (overlooking duties) as the Commanding Officer of the Regiment was selected to proceed overseas to follow a course of training. With the change of command the Battalion was moved to Mannar District.
On 31st March 1991 troops set off from the Thalladi Camp in Mannar, launching 'Operation Tiger Chase' with the objective to destroy the terrorist bases in Weppamkulam, Silawathurai, and Kokkupadayan in the Mannar District thus, facilitating control of the Vavuniya - Mannar highway. This saw the clearing of the LTTE bases in the area of along with the killing of a large number of terrorists and the capture of a considerable stock of munitions.
On 2nd May 1991 with the participation of troops from the 1st Battalion Sri Lanka Light Infantry, 3rd Battalion Sri Lanka Light Infantry, 1st Battalion Sri Lanka Sinha Regiment, 1st Battalion Gajaba Regiment and 3rd Battalion Gajaba Regiment, 'Operation Wanni Wickrama' was launched under the direction of Major General Denzil Kobbekaduwa while Colonel Shantha Kottegoda led it. On successful completion the areas of Nanviyalam, Nochimotei, Omanthai and Kokilai in the Vavuniya District were brought under the control of the Army. Moreover, the 'Ramesh Base' and the '37 Base' along with other main camps of terrorists had in the Omanthai area were destroyed. A number of terrorists were killed and a large quantity of arms and ammunition along with a few bulldozers and military equipment were captured.
'Operation Wanni Wicrama II' was launched on 14th June 1991 with the participation of the temporarily formed 'Wikum Brigade', the aim being to destroy the LTTE camps in the Pandichirichan area in the Mannar District. Troops of the Sinha Battalion were led by Major P Paniipitiya. The operation went on for nine days at the end of which the Army gained many successes. On completion of the operation, on 22nd June, the troops returned.
On 10th July 1991 at 0420 hrs the Elephant-Pass Camp manned by the 6th Battalion Sri Lanka Sinha Regiment came under an enemy attack. The camp was under siege for a number of days and the terrorists from time to time tried to overrun the camp. At the time the 6th Battalion Sri Lanka Sinha Regiment was commanded by Major SG Karunarathna. 'Operation Balavegaya' was launched to break the siege and to rescue the troops besieged. Troops from the 1st Battalion Sri Lanka Sinha Regiment took part in 'Balavegaya' under the command of their Commanding Officer Major P Pannipitiya. 18th August 1991 saw the successful completion of the operation with the rescue of the troops who were trapped. A large number of terrorists were killed and a large haul of arms were taken into custody. An officer & 20 other ranks were killed while 6 officers & 104 other ranks were wounded in action. On completion of the operation the Battalion was moved to Welioya via Pulmudai, by sea.
Aimed at destroying the One-Four Base of the LTTE deep inside the Mullaitivu jungles, 'OperationAkunupahara' was launched on 29th August 1991 with Sinha troops being part of it. The LTTE base as well as smaller camps surrounding the base; namely Sathis, Sugathan, Michael and Sodia camps were destroyed with a considerable number of terrorists being killed. Fourteen were killed in action while six officers and 85 other ranks received injuries out of which an officer and thirteen other ranks lost their legs by stepping on anti-personnel.
On 8thFebruary 1993, Lieutenant Colonel P Pannipitiya relinquished duties of Commanding Officer while Major WMS Gunaratne took over same.
On 19thFebruary 1993, the 'B' Company camped in Pesalai and Mannar town.
The 'D' Company received training from the Sri Lanka Armoured Corps on armour infantry movement.
On 30th April 1993 MajorSG Karunaratna having returned from overseas took over the command of the Regiment from Major WMS Gunaratna who (temporarily) performed duties in the appointment of Commanding Officer.
On 19th September 1993 the Commanding Officer Major SG Karunaratna psc with troops from the Battalion reported to the Vettilaikerni Camp to take part in 'Operation Yaldevi'. Being the forward most battalion on the offensive, it contributed significantly towards accomplishing its operational mission.
On completion of the operation, on 4th October 1993, the Battalion moved to Elephant Pass and then to Monkey Bridge Camp at Trincomalee by sea reaching Monkey Bridge on the 10th. In Trincomalee, the 'A' Company was stationed at Koviladi, 'B' Company at Kandalkadu, 'C' Company at Wilgamwehera while the 'D' Company was stationed at Palanpatar.
