Singapore strategy
The planners thought that a war with Japan would have three phases: while the garrison of Singapore defended the fortress, the fleet would make its way to Singapore, so that it could relieve or recapture Hong Kong. The fleet could also  impose a blockade on the Japanese home islands, which would force the Japanese to accept terms. The planners did not think it was practical to invade Japan. The planners also thought that the Japanese would fight a naval battle. Japan consists of many islands. The planners therefore thought that economic pressure would be enough.