Sanshikidan was a form of ammunition: a World War II-era combined shrapnel and incendiary anti-aircraft round used by the Imperial Japanese Navy. The type of layered construction of the warheads were generically referred to as Beehive rounds. The shells were intended to put up a barrage of flame through which any aircraft attempting to attack would have to navigate. However, U.S. pilots considered these shells to be more of a pyrotechnics display than an effective anti-aircraft weapon.