After attending the Rashtriya Indian Military College (RIMC), he gained commissioned as a Midshipman in the Royal Indian Navy in 1941 in the Executive Branch. He participated in the World War II as an officer in the Royal Indian Navy on the behalf of the United Kingdom on the European front, and was sent to attend the Britannia Royal Naval College after the end of World War II in 1945. After graduating in the staff course degree, he returned to British India and subsequently promoted as Lieutenant in the Royal Indian Navy and decided to opt for Pakistan as an aftermath of partition of British India, also the same year. Hassan was among the first twenty naval officers who decided to join the Royal Pakistan Navy (RPN) as a Lieutenant with a Service number PN.0073 that was listed in the seniority list sent by the Royal Indian Navy to Pakistan's Ministry of Defence. He was said to be an excellent hockey player in the navy where he captained the navy's hockey team against the Indian Navy's hockey team; the RPN's hockey team won by a margin of five goals to one secured against RIN's team.