that year's Grand Joint Army-Navy Exercise. Fleet Problem III was also the first which USS Langley (CV-1) took part in, replacing some of the simulated aircraft carriers used in Fleet Problem I. Fleet Problem IV The 1924 series culminated with Fleet Problem IV, running from January 23rd to February 1st. Designed to simulate offensive amphibious operations against Japan, the Blue Fleet was based in Panama -- simulating US forces based in the Philippines -- while the Black Fleet, made up of the Special Service Squadron, was tasked with defending Puerto Rico -- simulating Japanese defenders of Okinawa. Over the week of gameplay, Black aircraft attacked Blue forces consistently, but failed to prevent an amphibious landing - which allowed the US Marine Corps to test their new landing craft, Christie amphibious tanks, and combat logistics techniques. Fleet Problem IV met with serious criticism for having high levels of notional units - units that existed on paper, not in real life. Nearly 10% of Blue's ships and almost 70% of Black's forces were simulated. Vice Admiral Newton McCully argued that "In all exercises, constructive forces or features should be reduced to a minimum," and no later Fleet Problem used the same high level of simulated forces. Fleet Problem V and Grand Joint Army-Navy Exercise No. 3 Fleet Problem V ran from February 23rd to March 12th of 1925, forming the first third of a multi-month sequence of deployments that lasted until October. The Black force, the aggressor, was formed from the United States Battle Fleet, including the US' first aircraft carrier, along with two seaplane tenders. The Blue force, formed out of the Scouting Force, enjoyed only about 30 floatplanes, half of which were fictional. Even these were limited, since the floatplanes aboard Blue forces' battleship could not be launched for lack of a working catapult. The two fleets made only limited contact on March 10, when several Blue force submarines spotted and attacked the Black fleet, before being sunk by Blue escorts. Langleys positive performance helped speed the completion of aircraft carriers and . While returning to San Francisco and transiting to Hawaii, the fleet was followed closely by the Japanese tanker Hyatoma Maru, leading the fleet to tighten its communication security in an attempt to prevent espionage. One aspect of Fleet Problem V was conducted near Guadalupe Island off Baja California and involved attacking a lightly held position and refueling