The Japanese army commenced its full invasion of China in July 1937 and finally conquered Hong Kong in December 1941. Local residents had to live through three years and eight months of harsh occupation.

Postal services were resumed in Japanese-occupied Hong Kong in early 1942, and when the post offices reopened, the public found that Hong Kong stamps had been replaced by definitive stamps from Japan, which came in 21 denominations ranging from 0.5 sen to 10 yen. However, because there were no differences between the definitive stamps used in Hong Kong and Japan at that time, postmarks were the only way to tell them apart. Hong Kong was also forced to use military yen as its currency during the occupation, and local postage rates increased from 4 sen in 1942 to 3 yen (equivalent to 12 Hong Kong dollars) at the end of the war in 1945, bearing testimony to the depreciation that the Japanese military yen underwent. The Japanese army also applied surcharges on three stamp issues, the low values of which had made them virtually useless, to cope with the high postage resulting from hyper-inflation.

After Emperor Hirohito announced Japan’s unconditional surrender on 15 August 1945, Britain resumed its administration of Hong Kong under a provisional government. Although local mail services recommenced on 25 August, they were limited because of a severe lack of both stamps and wooden chops for postmarks, and no postage was charged in this interim period. In early September, however, the Military Government under Rear-Admiral Harcourt discovered a stock of pre-war stamps in the vaults of the General Post Office and the Hongkong and Shanghai Banking Corporation. At the same time, stores that had been sent to Australia and South Africa for safekeeping during the war gradually arrived back in the colony, and Hong Kong stamps went on sale again on 28 September 1945, marking the return of normal postal services.