The time period in the last few years of Singapore’s Straits Settlements history leading up to the Japanese occupation was an interesting one, with the impending and inevitable threat of war on the crown colony; well understood by the British forces when World War II broke out in 1939. The increases in military operations meant that communications had to be expedient and effective during those tumultuous period. Presented here from my collection are two very scarce “On Active Service” covers that had never seen the light of the day in most philatelic records of the region. These covers were usually used without postage stamps and were sent by military officers “On Active Service”. The airforce cover on the left bears postmark of cancellation at Field Post Office (F.P.O.) at S.P. 501 on 18 April 1941. It was censored by R.A.F. (Royal Air Force) 3 Type Red. The cover was addressed to the Municipal Treasurer at the Municipal Office. These Municipal Offices were housed in the former City Hall, now part of The National Gallery. The other navy cover on the right bears cancelled at F.P.O. S.P.501 on 1 July 1941. It was censored by H.M.S. (Her Majesty’s Ship) on 2 July 1941 with the officer’s signature. The cover was also addressed to the Municipal Office, specifically at the Revenue Division to the Assistant Treasurer. Not long after the war, the F.P.O. in South East Asian command was officially closed on April 13 1947.