The Gilbert and Marshall Islands campaign began on 20 November 1943 with the U.S. invasion of Tarawa and of Makin in the Gilbert Islands. That day, "I-40" and the submarines , , , , , , , and all received orders to proceed to the Gilberts and oppose the invasion. "I-40" got underway from Truk on 22 November 1943 to begin her first war patrol, assigned a patrol area off Makin Island. The Japanese never heard from her again.