Japanese Aerial-Burst Bombs

Further intelligence reports on Japanese aerial-bombs used against Allied bombers:


This article briefly outlines information received from the South Pacific regarding Japanese aerial-burst incendiary bombs.

At the present time two types of Japanese bombs are known which are designed to give aerial bursts. These bombs correspond with descriptions by pilots of bombs dropped on flights of our planes.


The 32-kilogram (70-pound) Model 99 high-explosive incendiary bomb appears to be the most commonly used type. This bomb is equipped with an impact nose fuse and a mechanical time tail fuse. The body of the bomb contains 198 incendiary pellets of steel filled with phosphorus and the tail contains 3J pounds of high explosive. On explosion the incendiary pellets shoot downwards in the form of a cone with an estimated danger radius of 50 to 75 yards. In addition to the incendiary effect of these pellets the bomb case supplies a fragmentation effect though probably not extending beyond 75 yards.

The bomb has angled tail fins which cause it to spin in the air.


The 250-kilogram (550-pound) high-explosive incendiary bomb is Type 2, Mark 3, Model 1. It is equipped with an impact nose fuse and mechanical time tail fuse. The bomb contains 73 pounds of high explosive and 756 incendiary fragments. On explosion fragments are sprayed conically downwards with great force to a range of 200 yards. Due to its angled tail fins this bomb also spins in the air.


The aerial-burst fuses used by the Japanese are all mechanical time fuses. Settings cannot be made in the airplane. The fuses do not arm until the bomb spins at the rate of 1,000 revolutions a minute. To attain this rate of spin the 250-kilogram bomb requires a drop of 3,000 feet and, therefore, must be released at this altitude or higher to insure a burst. The 32-kilogram bomb requires a similar drop. They may be set, however, to drop much greater distances before bursting.


Captured documents indicate that bomb clusters may be used against aircraft in flight. One type contains 76 bombs each weighing two-thirds of a pound while another variety contains 40 two-pound bombs. These bombs detonate on impact and are of the hollow charge variety.

For additional intelligence reports on German and Japanese use of aerial bombs against Allied bombers, see:


Aerial Bombs

WW2 Air Force Tactical IntelligenceThe following tactical intelligence report appeared in “Eastern Air Command Weekly Intelligence Summary”, No. 10, Nov. 3, 1944 published by Headquarters Eastern Air Command, Southeast Asia.

Oscars Drop Aerial Bombs on B-24 Moulmein Mission

22 October Preliminary Report from 356 Squadron (RAF)

Thirteen Liberators (B-24s) dropped bombs on Moulmein between 1159 and 1202 hours from 2000 feet to 2500 feet. Immediately after this attack two enemy aircraft; one Oscar and one Tojo, were sighted at two oclock, 2000 yards away and 500 feet above. One of these rolled off the top and dived through the first formation. (The Liberators were in two formations, 2000 yards apart – ahead and astern.) As it dived, enemy aircraft fired and hitting aircraft “D” inflicted slight damage to that machine’s leading and trailing edges. Enemy aircraft leveled off at 1000 feet.

The second of these two enemy aircraft stood off at 2000 yards then disappeared in the direction of Rangoon, performing aerobatics as it went on it’s way.

Two Oscars (MK II) were sighted 37 minutes after leaving the target area. Standing off, they remained in sight of the squadron for 35 minutes. At 1314 hours in position 1630 N 9500 E these two enemy aircraft split up and attacked simultaneously. The Liberators were now at 10,000 feet.

Attacking from ahead and above, one enemy aircraft dived and dropped what appeared to be aerial bombs which seemed to flutter down slowly in pairs. One bomb burst with a reddish yellow flash in front of and below the Oscar while it was still diving, but no damage was done to our aircraft.

The second Oscar came in level from astern. It closed to 250 yards but did not fire. Two rear gunners and one mid-upper gunner opened lire and tracer from aircraft “J” appeared to enter the Oscar’s wings. Enemy aircraft broke away apparently undamaged….

Jap T/E Fighter Drops Aerial Bomb on Truk Strike

Thirteen B-24s bombed N Moen Airfield, Truk, from 19,500 feet on 19 September 1944. A twin-engine Jap fighter attacked the formation and dropped a phosphorous aerial bomb. (7th AF Intelligence Summary No. 53, 7 October, 1944).

The attack was made at noon and was unescorted. One minute after “bombs away” our planes were intercepted by 3-4 Zekes and one possible Nick. One two-plane coordinated attack was made from one oclock high. Both of these planes dropped aerial bombs, after coming in from out of the sun. This attack was followed by five individual passes from between twelve and two oclock. These fighters also came in high and released three aerial bombs and made two shooting passes. The bombs hit low and wide.

One of our planes had a feathered engine and was subjected to two fairly aggressive attacks from five and eight oclock high. However, the formation protected this plane by slowing down and keeping him well covered.

The twin-engine fighter came in from the nose, high and out of the sun, and pressed his attack to 250 yards. He broke away to the right at two oclock, exposing the belly of the plane. A phosphorous bomb was dropped, bursting approximately 300 yards at three oclock. Although twin-engine fighters have been seen on many previous missions, this aerial bomb attack is the first reported from this type fighter. (Illustration A).

Japanese Aerial Bombs in WW2

Zekes Coordinate on Aerial Bomb Attack

Fifteen more B-24s hit the same target. (See story above). The attacks were coordinated so that after “bombs away” the two formations gave mutual support. Separate bomb runs split the AA defenses.

Interception of this second formation was started just before the bomb run. Three Zekes made a coordinated attack, two coming in trail from 11 oclock high and the third diving steeply from out of the sun. The first pass was a shooting pass, the second was an aerial bomb attack, and the third was an aerial bomb and shooting pass. The first fighter broke away at 500′ rolling down toward 5 oclock. His trailing wingman also broke off the attack at 500 feet and pulled off toward 3 oclock low. The Zeke that dove out of the sun, reached a position about 600′ in front of the formation but then pulled up and rolled into a spiral breakaway above the formation.

Both of the aerial bombs released in this coordinated attack were a new type. (Illustration B). One of the bombs was observed prior to bursting and was described 1½ feet in diameter, 6 feet long and spinning to the left as it fell. The burst was orange-red and shrapnel was thrown out which looked like tracers. Both bombs were accurate as to altitude. One burst to the left and one to the right of the formation. One burst was close enough to No. 2 plane in B-Flight for the blast to jar loose lighting fixtures in the cockpit.

All other passes were very unaggressive. The mission was notable since after leaving the target, all 27 planes offered mutual support instead of the two formations leaving separately. The 431st crew members expressed the opinion that this may have been responsible for the unusually unaggressive tactics on the part of the enemy pilots. No damage to our aircraft resulted from enemy fire.

For additional intelligence reports on German and Japanese use of aerial bombs against Allied bombers, see: