For the time being, the fleet was crippled. The Japanese knew they would lose naval supremacy by 1943. An attack against the US had to be made before it was too late. A short war between Japan and Russia in 1939 deflected Japanese attention southward toward Australia instead of westward into Asia. Japan had to eliminate US sea power before it could turn on oil, rubber and tin regions of Indonesia and Malaysia.
Japan is an island country lacking in natural resources.
The militarists believed that Japan had to widen the arc of the Greater East Asian Co-prosperity sphere if it was to survive as a nation. Over the next 6 months it appeared that Japan could not be stopped. Not until Midway, June 1942, did was Japan handed its first defeat. Congress set the paper strength of the Regular Army at 600,000. The act came after the news that German forces had defeated France in a campaign that lasted only 6 weeks.