Japanese Rocket Artillery

A Japanese Type 4 20mm rocket and launcher - US National Archives

The Japanese had been slow to adopt the rocket as an artillery piece when compared to other major powers, such as Germany and the United States, but that did not mean that such weapons did not exist in the inventory of the Imperial Army. As the Americans advanced on Manila, several types of Japanese rocket artillery were available to Admiral Iwabuchi’s Manila Naval Defense Force, including the Army’s Type 4 200mm rocket mortar and the Navy’s 450mm rocket mortars. These, along with others, had seen increased development due to the ease of manufacture as opposed to similar caliber artillery, as the rockets required only a relatively thin launch rube due to the substantially lower pressures involved with firing of a rocket as opposed to a conventional cannon.

Other types used an aircraft bomb fitted with a rocket motor and fired from a simple wooden launching rail, and these types of bombs were readily available from the surrounding airfields, most of which were now disused as the Americans had all but destroyed Japanese air power in the Philippines. The weapons had already seen limited use in the previous year on various battlefields, and were known for the demoralizing effect of the rockets, as they made a distinctive sound as they descended on their target, leading to the American use of the term “Screaming Mimi”, first popularized for the German Nebelwerfer used in Europe, now spreading to the Pacific as well.