Percival was made a full colonel in March 1936, and until 1938 he was General Staff Officer Grade 1 in Malaya, the Chief of Staff to General Dobbie, the General Officer Commanding in Malaya. During this time, he recognised that Singapore was no longer an isolated fortress. He considered the possibility of the Japanese landing in Thailand to "burgle Malaya by the backdoor and conducted an appraisal of the possibility of an attack being launched on Singapore from the North, which was supplied to the War Office, and which Percival subsequently felt was similar to the plan followed by the Japanese in 1941. He also supported Dobbie's unexecuted plan for the construction of fixed defences in Southern Johore. In March 1938, he returned to Britain and was (temporarily) promoted to brigadier on the General Staff, Aldershot Command.