Thunder Gods

Text: Jan Bobek

Illustration: Piotr Forkasiewicz

Cat. No. 84211

If any aviation weapon has come to symbolize the special attack operations of the Japanese armed forces in the closing stages of the Second World War, for many readers it is undoubtedly the rocket-powered MXY-7 Ōka (“cherry blossom”).

In August 1944, design work was approved for a rocket aircraft carrying a 1,200 kg warhead. Propulsion consisted of three rocket motors, each producing 2.62 kN of thrust, supplemented by auxiliary units on the wings. A glider version was ready for flight testing by October 1944. The rocket-powered Model 11 was intended for launch from modified G4M Betty bombers. As the pilot lacked an oxygen system, the carrier’s slow pre-launch approach had to be flown at 10,000 feet. This restricted the powered and subsequent glide phase to a maximum range of 18 nautical miles (33.3 km), forcing the mother aircraft to fly much of the approach within areas patrolled by enemy fighters. With access to German rocket technology, of which the Japanese had only limited knowledge, the Ōka’s range would have been significantly greater.

Kōkūtai 721 was established for operational deployment of the Ōka Model 11, while Kōkūtai 722 was formed to train its pilots. This unit was also intended to operate the smaller Ōka Model 22, planned for launch from P1Y Ginga (Frances) bombers, but the concept was abandoned after unsuccessful initial tests. Later, Kōkūtai 725 was created to deploy a larger Ōka variant designed for catapult launch from land bases in Japan’s mountainous regions. This was the MXY-7 Model 43 Otsu, planned to use the same turbojet engine as the twin-engine Kikka bomber, already intended for the Ōka Model 22. From the naval aviation perspective, the Ōka was regarded not as an aircraft but as a weapon, accordingly, it carried no national insignia (hinomaru), usually bearing only a unit and an individual number.

The IJN sought to deliver Ōka aircraft to the Philippines, Taiwan, and Okinawa to ensure sufficient stocks for mass deployment. During these transport efforts (including other cargo) Japan lost two aircraft carriers. Smaller vessels were also used for transport, and the Americans first encountered the Ōka on 1 April 1945 after capturing an airfield on Okinawa. The captured aircraft received the Allied reporting name “Baka,” a Japanese pejorative meaning “fool” or “idiot.” One theory holds that intelligence officers chose the name based on the assumption that only a madman would pilot such a machine, another suggests it was inspired by the date - April Fools’ Day.

Japanese aviators were certainly no fools. They were predominantly volunteers, in many cases veterans, who saw self-sacrifice in a ramming attack as a more effective means of inflicting damage on heavily defended naval formations, missions from which the chances of return were minimal in any case.

Kōkūtai 721, established in October 1944, was given the name Jinrai, often translated as either “Divine Thunder” or “Thunder Gods.” The Ōka aircraft were organized into four flights and for a time even had their own fighter escort unit. The carrier aircraft were G4M Betty bombers from Hikōtai 708 and 711, while fighter cover was provided by A6M Zero pilots from Hikōtai 305, 306, and 307. The principal operational base became Kanoya. Two-seat Zero variants were assigned to various elements of Kōkūtai 721, including the Ōka flights.

Both training and operational deployment were plagued by numerous organizational, technical, and tactical problems. Some Ōka pilots were committed repeatedly due to aborted missions, while many G4M bombers were shot down by American fighters. Several Ōkas were destroyed by defensive fire from U.S. warships, one destroyer was even credited with shooting down two.

On 12 April 1945, Ōka pilots sank the destroyer USS Mannert L. Abele. During various missions, over the next two months, they damaged seven other vessels. Kamikaze operations also included pilots from Hikōtai 306 flying Zero fighters. In addition to the twelve Ōka missions, approximately 200 kamikaze aviators from this unit sacrificed their lives in Zeros, primarily within the Kenmu-tai. Many had originally been trained for Ōka operations, but due to shortages of G4M carriers were forced to fly Zeros. Kōkūtai 721 later coordinated kamikaze operations of other units as well.

Kōkūtai 721 was the largest kamikaze unit in terms of personnel. Within its ranks, 369 pilots of single-seat aircraft and 365 crew members of Betty bombers were killed. Their tragic fate is commemorated by several memorials. The story of this unit is compellingly told by Dan King in his fascinating book Blossoms from the Sky. It is highly recommended, having been written in cooperation with surviving veterans of the unit and relatives of deceased or killed unit members.