AA mine discharger Wikipedia
The AA mine discharger was a Japanese anti-aircraft weapon of the Second World War. The device was a simple tube like an infantry mortar of 70 mm or 81 mm caliber. Instead of a standard mortar bomb, the projectile was a tube containing seven individual mines, each approximately 11/16ths of an inch in diameter (18 mm) and 3 inches (76 mm) long. Each mine was equipped with its own parachute. When fired, the mortar threw the shell to a range of 3,000 to 4,000 feet (900 to 1,200 m) and a maximum altitude of approximately 600 m. The shell ejected the mines at the top of its arc. They would then float down on their parachutes. They were fused to detonate on contact or after a fixed time period, damaging nearby aircraft. The projectile could alternatively be launched using a standard Type 11 70 mm infantry mortar.
The weapon could also be used like a simple cluster bomb, by firing over enemy troops.