The 20th Battalion Sri Lanka Sinha Regimentwas formed on 22nd October 2008 at the Vavunikulam National School and Lieutenant Colonel UD Wijesekara RSP psc was appointed as its first Commanding Officer.
The battalion was moved to Iyankulam on 31st October 2008 and placed under command to the 632 Brigade as part of the Task Force 3. The Battalion's Tactical Headquarter shifted to Olumadu on 6th December 2008 and the troops were deployed as part of the operations launched to regain control of the A9 road that was at the time being held by the LTTE.
The Battalion was part of the larger group that was involved in the capturing of the LTTE's airfield at Iranamadu on 24th December 2008.
On 7th February 2009 the Battalion was air lifted to Mullaitivu and was placed under the 592 Brigade of the 59 Division and deployed on the offensive to retake Nandikadal.
With the end of the 'Humanitarian Operation', the Battalion on 2nd June 2009 setup camp inMannakulam Village in Mankulam.
On 5th March 2010 Lieutenant Colonel JDA Gunasekara was appointed as the Commanding Officer.
On 13th April 2010 the Battalion headquarters shifted to Kumakulam area which was under 612 Brigade and was engaged in assisting the Internally Displaced Persons (IDPs).
On 21st November 2012 Lieutenant Colonel ARSSUIB Angammana was appointed as the Commanding Officer.
On 18th March 2013, the Battalion Headquarters was moved to Periyawalayankaddu in the Mannar District.
Since the inception of the battalion in 2008 it has done an admirable service during "Humanitarian Operation" and after the operation to resettle displaced civilians which carries to enhance the image of the battalion and as a whole the image of the Sinha Regiment.
