Japanese aircraft carrier Chiyoda

The 2nd Naval Armaments Supplement Programme otherwise known as the "Circle Two" Plan was the second of four expansion plans of the Imperial Japanese Navy between 1930 and the start of World War II.

Naval aviation is the application of military air power by navies, whether from warships that embark aircraft, or land bases.

The Washington Naval Treaty, also known as the Five-Power Treaty, was a treaty signed during 1922 among the major Allies of World War I, which agreed to prevent an arms race by limiting naval construction. It was negotiated at the Washington Naval Conference in Washington, D.C. from November 1921 to February 1922 and signed by the governments of the United Kingdom, United States, France, Italy, and Japan. It limited the construction of battleships, battlecruisers and aircraft carriers by the signatories. The numbers of other categories of warships, including cruisers, destroyers, and submarines, were not limited by the treaty, but those ships were limited to 10,000 tons displacement each.

The London Naval Treaty, officially the Treaty for the Limitation and Reduction of Naval Armament, was an agreement between the United Kingdom, Japan, France, Italy, and the United States that was signed on 22 April 1930. Seeking to address issues not covered in the 1922 Washington Naval Treaty, which had created tonnage limits for each nation's surface warships, the new agreement regulated submarine warfare, further controlled cruisers and destroyers, and limited naval shipbuilding.

The knot is a unit of speed equal to one nautical mile per hour, exactly 1.852 km/h. The ISO standard symbol for the knot is kn. The same symbol is preferred by the Institute of Electrical and Electronics Engineers (IEEE), while kt is also common, especially in aviation, where it is the form recommended by the International Civil Aviation Organization (ICAO). The knot is a non-SI unit. The knot is used in meteorology, and in maritime and air navigation. A vessel travelling at 1 knot along a meridian travels approximately one minute of geographic latitude in one hour.

The Kawanishi E7K was a Japanese three-seat reconnaissance seaplane mainly in use during the 1930s. It was allocated the reporting name Alf by the Allies of World War II.

The Nakajima E8N was a Japanese ship-borne, catapult-launched, reconnaissance seaplane of the Second Sino-Japanese War. It was a single-engine, two-seat biplane with a central main-float and underwing outriggers. During the Pacific War, it was known to the Allies by the reporting name "Dave".

A floatplane is a type of seaplane with one or more slender floats mounted under the fuselage to provide buoyancy. By contrast, a flying boat uses its fuselage for buoyancy. Either type of seaplane may also have landing gear suitable for land, making the vehicle an amphibious aircraft. British usage is to call "floatplanes" "seaplanes" rather than use the term "seaplane" to refer to both floatplanes and flying boats.

The 12.7 cm/40 Type 89 naval gun was a Japanese anti-aircraft (AA) gun introduced before World War II. It was the Imperial Japanese Navy's standard heavy AA gun during the war.

A steam turbine is a machine that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft. Its modern manifestation was invented by Charles Parsons in 1884. Fabrication of a modern steam turbine involves advanced metalwork to form high-grade steel alloys into precision parts using technologies that first became available in the 20th century; continued advances in durability and efficiency of steam turbines remains central to the energy economics of the 21st century.

Horsepower (hp) is a unit of measurement of power, or the rate at which work is done, usually in reference to the output of engines or motors. There are many different standards and types of horsepower. Two common definitions used today are the mechanical horsepower, which is about 745.7 watts, and the metric horsepower, which is approximately 735.5 watts.

The Battle of Midway was a major naval battle in the Pacific Theater of World War II that took place from 4–7 June 1942, six months after Japan's attack on Pearl Harbor and one month after the Battle of the Coral Sea. The U.S. Navy under Admirals Chester W. Nimitz, Frank J. Fletcher, and Raymond A. Spruance defeated an attacking fleet of the Imperial Japanese Navy under Admirals Isoroku Yamamoto, Chūichi Nagumo, and Nobutake Kondō north of Midway Atoll, inflicting devastating damage on the Japanese fleet. Military historian John Keegan called it "the most stunning and decisive blow in the history of naval warfare", while naval historian Craig Symonds called it "one of the most consequential naval engagements in world history, ranking alongside Salamis, Trafalgar, and Tsushima Strait, as both tactically decisive and strategically influential".

Laying the keel or laying down is the formal recognition of the start of a ship's construction. It is often marked with a ceremony attended by dignitaries from the shipbuilding company and the ultimate owners of the ship.

Kure Naval Arsenal was one of four principal naval shipyards owned and operated by the Imperial Japanese Navy.

The Combined Fleet was the main sea-going component of the Imperial Japanese Navy. Until 1933, the Combined Fleet was not a permanent organization, but a temporary force formed for the duration of a conflict or major naval maneuvers from various units normally under separate commands in peacetime.

The Second Sino-Japanese War (1937–1945) or War of Resistance was a military conflict primarily between the Republic of China and the Empire of Japan. The war made up the Chinese theater of the wider Pacific Theater of the Second World War. The beginning of the war is conventionally dated to the Marco Polo Bridge Incident on 7 July 1937, when a dispute between Japanese and Chinese troops in Peking escalated into a full-scale invasion. Some Chinese historians consider the start of the war as the Japanese invasion of Manchuria on 18 September 1931. China was aided by the Soviet Union, the United Kingdom, the United States, and Nazi Germany before its alliance with Japan. Around 20 million people, mostly civilians, were killed.

Kamoi was an oiler/seaplane tender/flying boat tender of the Imperial Japanese Navy, serving from the 1920s through World War II. She was initially planned in 1920 as one of six of the oilers under the Eight-eight fleet final plan.

Chuuk Lagoon, previously Truk Atoll, is an atoll in the central Pacific. It lies about 1,800 kilometres northeast of New Guinea, and is part of Chuuk State within the Federated States of Micronesia (FSM). A protective reef, 225 kilometres (140 mi) around, encloses a natural harbour 79 by 50 km, with an area of 2,130 km2 (820 sq mi). It has a land area of 93.07 square kilometres, with a population of 36,158 people and a maximal elevation of 443 metres (1,453 ft). Weno city on Moen Island functions as both the atoll's capital and the state capital, and is the largest city in the FSM with its 13,700 people.

The attack on Pearl Harbor was a surprise military strike by the Imperial Japanese Navy Air Service upon the United States against the naval base at Pearl Harbor in Honolulu, Territory of Hawaii, just before 8:00 a.m. on Sunday, December 7, 1941. The United States was a neutral country at the time; the attack led to its formal entry into World War II the next day. The Japanese military leadership referred to the attack as the Hawaii Operation and Operation AI, and as Operation Z during its planning.

The 6th Fleet was a fleet of the Imperial Japanese Navy (IJN) that during World War II, had primary responsibility for the command of submarine operations.

The Battle of Midway was a major naval battle in the Pacific Theater of World War II that took place from 4–7 June 1942, six months after Japan's attack on Pearl Harbor and one month after the Battle of the Coral Sea. The U.S. Navy under Admirals Chester W. Nimitz, Frank J. Fletcher, and Raymond A. Spruance defeated an attacking fleet of the Imperial Japanese Navy under Admirals Isoroku Yamamoto, Chūichi Nagumo, and Nobutake Kondō north of Midway Atoll, inflicting devastating damage on the Japanese fleet. Military historian John Keegan called it "the most stunning and decisive blow in the history of naval warfare", while naval historian Craig Symonds called it "one of the most consequential naval engagements in world history, ranking alongside Salamis, Trafalgar, and Tsushima Strait, as both tactically decisive and strategically influential".

Kure Atoll or Ocean Island is an atoll in the Pacific Ocean 48 nautical miles west-northwest of Midway Atoll in the Northwestern Hawaiian Islands at 28°25′N 178°20′W. A coral ring six miles across encloses a lagoon several meters deep. The only land of significant size is called Green Island and is a habitat for hundreds of thousands of seabirds. A short, unused and unmaintained runway and a portion of one building, both from a former United States Coast Guard LORAN station, are located on the island. Politically, it is part of Hawaii, although separated from the rest of the state by Midway, which is a separate unorganized territory. Green Island, in addition to being the nesting grounds for tens of thousands of seabirds, has recorded several vagrant terrestrial birds, including snow bunting, eyebrowed thrush, brambling, olive-backed pipit, black kite, Steller's sea eagle and Chinese sparrowhawk. It is currently managed as a Wildlife Bird Sanctuary by the State of Hawaii's Department of Land and Natural Resource–Division of Forestry and Wildlife as one of the co-trustees of Papahānaumokuākea Marine National Monument with support from the Kure Atoll Conservancy.

Midway Atoll is a 2.4 sq mi (6.2 km2) atoll in the North Pacific Ocean. Midway Atoll is an insular area of the United States and is an unorganized and unincorporated territory. The largest island is Sand Island, which has housing and an airstrip. Immediately to the east of Sand Island across the narrow Brooks Channel is Eastern Island, which is uninhabited and no longer has any facilities. Forming a rough, incomplete circle around the two main islands and creating Midway Lagoon is Spit Island, a narrow reef.