Akagi (“Red Castle”) was an aircraft carrier built for the Imperial Japanese Navy (IJN), named after Mount Akagi in present-day Gunma Prefecture. Though she was laid down as an Amagi-class battlecruiser, Akagi was converted to an aircraft carrier while still under construction to comply with the terms of the Washington Naval Treaty. The ship was rebuilt from 1935 to 1938 with her original three flight decks consolidated into a single enlarged flight deck and an island superstructure. The ship suffered fatal damage during the battle of Midway in WWII.
Based on a battlecruiser, Akagi was a unique-looking aircraft carrier. At the time of her construction, there were not many aircraft carriers in the navies around the world, hence there was no “standard design” at this early stage, which resulted in her unique configuration: triple-flight deck, unconventional port-side island, and six 8-in guns. Already being the most expensive ship in the Japanese fleet, she underwent an expensive refitting in 1935 that gave her the full-length flight deck configuration that she would enter the Pacific War with. The American pilots identified her as a carrier with a boxy superstructure and an improbably high flight deck that towered six stories above the main deck.
After the 1935 refitting, Akagi became the first Japanese carrier with a modern large flight deck, and it was the operational experiences aboard the Akagi that forged the Japanese naval airpower doctrine. She participated in every major action in the early part of the war, including Pearl Harbor, the attack against Port Darwin, operations in the Indian Ocean, and the Battle of Midway. Unfortunately, with her unique design came a unique weakness as well, and the weakness presented itself during the Battle of Midway. Aside from the fact that her anti-aircraft weaponry was of an older and slow-firing design, they were also positioned poorly. Her anti-aircraft batteries were positioned on the port and starboard sides of the ship, twenty or so feet below the flight deck, therefore guns on each side could only fire at targets on the same side of the ship. Additionally, port side guns are additionally blocked by the island, further reducing the effectiveness of the weapons. This was one of the many reasons why she was fatally attacked at Midway on 4 Jun 1942 at the hands of American dive bombers.
On 20 October 2019, deep-sea explorers of Vulcan Inc. operating off the vessel RV Petrel identified the wreck of Akagi using high-frequency sonar. Located 1,300 miles (2,100 km) northwest of Pearl Harbor, Akagi was found at a depth of 18,011 feet (5,490 m).