"Istukushima" was reactivated on 15 November 1940 under the Combined Fleet and resumed patrols of the China coast to April 1941, when she was reassigned back to the IJN 3rd Fleet and deployed to Palau in December 1941. At the time of the attack on Pearl Harbor in December 1941, "Itsukushima" was assigned to the Southern Philippines Striking Force of the IJN 3rd Fleet under the overall command of Admiral Ibō Takahashi, and tasked with mining the San Bernardino Strait.