On this day, february 19, at 02:00 in 1945, the formidable 16-inch battleship guns from USS North Carolina, USS Washington and later added USS West Virginia signaled the commencement of the invasion of Iwo Jima. American naval craft used nearly everything available in their arsenal to shell the island, from the main guns to the antiaircraft flak cannons to the newly developed rockets. Soon thereafter, 100 bombers attacked the island, followed by another volley from the naval guns. Although the bombing was consistent, it did not deter the Japanese defenses, since most of the Japanese positions were well-fortified and protected from shelling. Many were sheltered by Mount Suribachi itself, as the Japanese had spent the months prior to the invasion creating an elaborate system of tunnels and firing positions that ran throughout the entire mountain.