USS Ranger (CV-4)  USS "Ranger" (CV-4) was an interwar United States Navy aircraft carrier, the only ship of its class. As a Treaty ship, "Ranger" was the first U.S. vessel to be designed and built from the keel up as a carrier. It was relatively small, just long and under , closer in size and displacement to the first US carrier——than later ships. An island superstructure was not included in the original design, but was added after completion. Deemed too slow for use with the Pacific Fleet's carrier task forces against Japan, the ship spent most of World War II in the Atlantic Ocean where the German fleet, the "Kriegsmarine", was a weaker opponent. "Ranger" saw combat in that theatre and provided air support for Operation Torch. In October 1943, she fought in Operation Leader, air attacks on German shipping off Norway. The ship was sold for scrap in 1947. Work began in 1925 on the design of a fourth aircraft carrier for the US Navy, as a follow-on to the small , converted from a collier, and the large and , which were in the process of being converted from incomplete battlecruisers. Carrier number four was the Navy’s first opportunity to design a purpose-built aircraft carrier. Preliminary design work occurred before extensive operation of the preceding three. Having limited experience to draw on, key characteristics of the design were derived from wargaming experience at the U.S. Naval War College. During design and construction many alterations would occur as a result of increasing experience with "Langley, Lexington," and "Saratoga". The major limitation constraining any design was the Washington Naval Treaty of 1920. After "Lexington" and "Saratoga", there were remaining for construction of aircraft carriers. This resulted in modeling for three 23,000 long ton carriers, four 17,250 ton carriers, and five 13,800 ton carriers. Of the three sizes, the smaller 13,800 was selected because the five hulls would have the largest aggregate aircraft capacity. Wargames had indicated that severe attrition to airframes and hulls would occur in any war. The college’s solution was to maximize the number of aircraft and hulls allowable under the treaty. Initially, "Ranger" was designed as a flush-decker, like "Langley", with nothing extending above the flight deck. Keeping the flightdeck clear of obstacles complicated the arrangement of machinery.