How did U.S. submarines isolate Japan during World War II?

During World War II, U.S. submarines played a critical role in isolating Japan by systematically destroying its merchant marine fleet, which was essential for supplying its military garrisons and home islands.12

The U.S. submarine campaign in the Pacific was highly successful, primarily utilizing the Gato- and Balao-class submarines. These vessels were instrumental in sinking more than 80 percent of the 6,000,000 tons of shipping that Japan possessed at the start of the war, with submarines alone responsible for half of those losses. By severing these vital maritime supply lines, the U.S. Navy effectively "encircled" Japan, leaving its far-flung military bases isolated and unable to receive necessary resources. This attrition of merchant shipping forced the Japanese to expose their remaining surface fleet to destruction in desperate attempts to maintain their supply routes, further weakening their overall war effort.312