Admiral Sushil Kumar, a Nagercoilite Christian from Tamil Nadu, was a Chief of Naval Staff in the Indian Navy. His christian surname is Isaacs which he dropped as not to confuse his initial with his brother who is also in the Service. He is often said to instruct his men with a quote from the Holy Gita "Do thy duty, reward is not thy concern'" . He was one of the highest ranking Indian christians in the Indian armed services .

Admiral Sushil Kumar assumed charge of the Indian Navy, as the 16th Chief of Naval Staff, on 30 December 1998. A specialist in hydrography and amphibious warfare, he is also a qualified air warfare instructor. He has participated in the 1961 Goa Liberation and in both the Indo-Pakistan Wars of 1965 and 1971. As Director of Naval Operations, he was decorated with an Uttam Yudh Seva Medal for his exceptional conduct in Operation Pawan and in Operation Cactus (Liberation of Maldives). He was awarded the Naosena Medal (NM) for gallantry whilst in command of INS Ghorpad. He is an alumni of the National Defence College and was an instructor at the Defence Services Staff College, Wellington. His training abroad includes a deputation to the Royal Navy onboard HMS Dampier in 1963 and a course in amphibious warfare with the US Navy at Coronado, San Diego, in 1976.

Admiral Kumar has held operational commands and important posts such as the Vice Chief of Naval Staff, the Flag Officer Maharashtra Area, Commander of the Flotilla in Mumbai and Fortress Commander Andaman & Nicobar Islands. He was the Flag Officer Commanding-in-Chief of the Southern Naval Command in Kochi, before being appointed as the Chief of Naval Staff. During his tenure as CNS, Admiral Kumar was the highest-decorated 'serving' officer in the Indian Navy and upon his retirement on 29 December 2001, he completed 40+ years of distinguished service. He is a keen yachtsman and has the rare distinction as a Naval Officer to have played polo on the international circuit with an international rating of 4+ goals.