Senanayaka visiting the 1st battalion of the CLI at the Echelon Square and watching volunteers being trained to handle light machine guns. It continued to grow throughout the early period of the 20th century. In Sri Lanka gained independence from Britain, becoming a Dominion within the commonwealth and a year earlier Ceylon entered into the bi-lateral Anglo-Ceylonese Defence Agreement of This followed by the Army Act No.
The Defence Agreement of provided the assurance that British would come to the aid of Ceylon in the event it was attacked by a foreign power and provided British military advisers to build up the country's military. Brigadier James Sinclair , Earl of Caithness was appointed as general officer commanding Ceylon Army, as such becoming the first commander of the Ceylon Army.
The initial requirement was to raise an artillery regiment, an engineer squadron, an infantry battalion, a medical unit, and a service corps company. For much of the s the army was preoccupied with the task of building itself and training existing and new personal.
New officers were sent for training at Royal Military Academy, Sandhurst which continued until the s and both officers and other ranks were sent to specialist training courses in Britain, India, Pakistan and Malaya. There were no formations and all units were structured to directly function under the Army Headquarters.
However temporary field headquarters were to be formed at the time requirement arose. The first internal security operation of the Ceylon Army began in , code named Operation Monty to counter the influx of illegal South Indian immigrants brought in by smugglers on the north-western coast, in support of Royal Ceylon Navy coastal patrols and police operations.
The Army was mobilised to help the police to restore peace under provincial emergency regulations during the hartal , the Gal Oya Valley riots and in it was deployed for the first time under emergency regulations throughout the island during the Riots. To counter these common strikes several units were formed, who were employed in development work when there were no strikes. This attempted coup affected the military to a great extent, since the government mistrusted the military, it reduced the size and growth of the army, especially the volunteer force, with several units being disbanded.
In May , when Ceylon was proclaimed a republic and changed its name from the Dominion of Ceylon to the Republic of Sri Lanka, all Army units were renamed accordingly. The war escalated to the point where India was asked to intervene as a peacekeeping force. The war with the LTTE was halted following the signing of a ceasefire agreement in with the help of international mediation. However, renewed violence broke out in December and following the collapse of peace talks, the Army has been involved in the heavy fighting that has resumed in the north and east of the country.
The major operations conducted by the army eventually led to the recapture of Jaffna and other rebel strongholds.