almost all of the submarines were able to get underway before an attack. The qualities designed into the Salmons for their role as fleet submarines made them well suited for the war they found themselves fighting, but some shortcomings came up that were not apparent prior to the war. It came to be realized that the boats were going to spend a lot more time on the surface than what had been previously acknowledged. Thus the large bulk of the conning tower fairwater became a liability. It was too easily spotted by keen-eyed Japanese lookouts using their excellent binoculars. It was found that portions of the fairwater plating could be cut away both fore and aft of the bridge, greatly reducing the silhouette. This also had the desirable effect of creating mounting locations for 20mm Oerlikon autocannons, which were useful against aircraft and small surface targets. The timely development of radar in the USN proved to be a key factor in the eventual victory over the Imperial Japanese Navy, and its incorporation into the Salmons and other USN submarines gave them a critical advantage in detection and defense. The first sets became available within days of the war beginning, and they were introduced to the boats as they went into overhaul in 1942. The original Mark 21 3-inch (76 mm)/50 caliber deck gun proved to be too light in service. It lacked sufficient punch to finish off crippled or small targets quickly enough to suit the crews. It was replaced by the Mark 9 4-inch (102 mm)/50 caliber gun in 1943–44, in most cases removed from an S-boat being transferred to training duty. The Submarine Force relied heavily on the well-liked Salmons during the first two and a half years of the war, with some of them completing 15 war patrols before being assigned to training duties by 1945. Salmon barely survived a severe depth charging by Japanese escort ships on 30 October 1944. She was retired from combat duty and spent the rest of the war as a training boat. Skipjack was expended as a target twice postwar: once in the Operation Crossroads nuclear weapons tests at Bikini Atoll 25 July 1946, and again as a target for aircraft rockets off California 11 August 1948. See also Allied submarines in the Pacific War List of lost United States submarines Unrestricted submarine warfare Torpedo List of submarine classes of the