after japan bombed pearl harbor in the united states on december 7, 1941, the second sino-japanese war became part of world war ii. it became a part of the area of fighting called the china-burma-india theatre. the entrance of the united states into the war in asia meant that the chinese military forces started receiving lend-lease supplies from the british and americans over the burma road. this helped the chinese fight back and get much-needed modern weapons.