Japan launched two main attack waves against Pearl Harbor. The first wave reached Oahu shortly before 8 a.m. on December 7, 1941, followed by a second wave beginning at about 8:40 a.m.
The first wave carried the heaviest torpedo and armor-piercing attacks against ships in the harbor. It also struck airfields to prevent American aircraft from responding. The second wave concentrated heavily on ships and airfields that remained operational, while also attacking additional military targets around Oahu.
Japanese commanders considered sending a third wave against fuel storage, repair facilities, and submarine installations, but Vice Admiral Chuichi Nagumo decided not to do so. The decision remains a major subject in historical discussions because those facilities were crucial to the Pacific Fleet’s ability to recover. “Two waves” refers to the principal organized air strikes, not to every individual aircraft movement or reconnaissance flight connected with the operation.