America was both a sleeping giant and a hollow tree

The sleeping giant and hollow tree metaphors describe American long-term capacity alongside its vulnerability at the beginning of the war. The United States had the capacity to fill out its apparent strength, but had not yet done so. In this reading, Japan's early success exceeded expectations because American resistance repeatedly collapsed. Some Japanese voices welcomed those gains, while others worried that the speed of the advance was producing overextension. The interpretation distinguishes the promise of American mobilization from the strength available when the fighting began.