The Fleet Problems are a series of naval exercises of the United States Navy conducted in the interwar period, and later resurrected by Pacific Fleet around 2014. The first twenty-one Fleet Problems — labeled with roman numerals as Fleet Problem I through Fleet Problem XXI — were conducted between 1923 and 1940. They were usually once-a-year exercises in which U.S. naval forces would engage in mock battles. One or more of the forces would play the part of a European or Asian navy. They were the culmination of the Navy's annual training maneuvers. Fleet Problem XXII, scheduled for 1941, was canceled because of the rising tensions with Japan that led to the US' entry into World War II. Following the outbreak of war, Fleet Problems underwent a prolonged hiatus, with other names being used to describe large American naval exercises. However, the term was revived in the 21st century under Admiral Scott H. Swift, with Fleet Problem XXIII through XXVIII taking place in the Pacific from 2014 on. Interwar Fleet Problems Fleet Problem I Fleet Problem I was held in February and March of 1923, off the coast of Panama. 165 ships and nearly 40,000 men, sailing from both coasts of the United States, participated in the exercise. The newly formed US Battle Fleet, which constituted the attacking Black force, was tasked with attacking the Panama Canal. Shortly after the ships of the East Coast-based Scouting Fleet—which, playing the Blue Force, was tasked to defend the Panama Canal—transited the canal into the Pacific, Black Force launched a simulated air raid. Two battleships, USS New York (BB-34) and USS Oklahoma (BB-37) simulated aircraft carriers modeled after the under-construction USS Langley (CV-1). A single plane launched from Oklahoma—representing a 15-plane squadron—dropped 10 miniature bombs and theoretically "destroyed" the spillway of the Gatun Dam, ending the Fleet Problem. The exercise was widely regarded as a success, including by members of Congress and reporters who had observed the fleets in action, setting the stage for a repeated experimentation in future years. Fleet Problems II, III, IV Fleet Problems II, III, and IV all represented different phases of the same scenario, and took place within the same two months of 1924. Fleet Problem II Fleet Problem II, which ran from January 2nd to 15th, followed the movement of the Battle Fleet, designated as the "Blue Force", from its base on the West Coast to Panama.