Page "Military history of the United Kingdom during World War II" Paragraph 166

In Burma, the Japanese attacked in January, 1942-shortly after the outbreak of war.

However, they did not begin to make real progress until the fall of Malaya ( 31 January 1942 ) and of Singapore ( February, 1942 ).

After that, Tokyo could transfer large numbers of aircraft to the Burma front to overwhelm the Allied forces.