Fonseka had joined the Sri Lanka Army in 1970 and was commissioned as a second lieutenant in June 1971 and rose through the ranks while completing training stints across South Asia and in the United States and the United Kingdom. He saw extensive action throughout the 26-year civil war and over the years acquired a reputation as a tough battlefield commander and was often in the thick of the action in fighting against the Tamil Tigers, culminating in a term as Commander of the Army from 6 December 2005 – 15 July 2009. As commander, he oversaw the final phase of the Sri Lankan Civil War, which resulted in the total defeat of the militant Liberation Tigers of Tamil Eelam. He also survived an assassination attempt when an LTTE suicide bomber attacked his motorcade in April 2006. Following the end of the war Fonseka was promoted to a four star rank in the Sri Lanka Army, becoming the first serving officer to hold a four star rank. He has been described as Sri Lanka's most successful army commander.