The Mitsubishi J4M1 was an advanced interceptor produced for the Japanese Navy but that never progressed beyond the design stage. The J4M would have been a rather unusual aircraft. It was a twin-boom aircraft, with a Mitsubishi MK9D engine in a pusher position at the rear of the central nacelle. The low-mounted wings were towards the rear of the central nacelle, with the booms mounted below the wings. The J4M was expected to reach 437mph at 26,245ft and was to be armed with one 30mm and two 20mm cannon. The J4M was produced in response to an 18-Shi specification, designed in part to support the Kyushu J7W. This was an even more unusual aircraft, but still won the production contract, and became the only canard aircraft (with the main wings at the rear) to enter production during the Second World War. As a result work on the Mitsubishi J4M came to an end at the basic design stage.