The following notes on Japanese antiaircraft measures were obtained from U.S. observers
and from enemy documents.
Observers report that, until recent months, the antiaircraft defenses on Japanese naval
ships have been more accurate and more concentrated than the land-based antiaircraft
fire. This distinction is no longer true, the observers say, because of improvements
in the quantity and quality of land-based weapons.
The nature of antiaircraft fire over enemy targets can frequently be predicted by evaluating
certain factors concerning the target. For example, if the target has tactical or
economic importance but is far distant and has not been visited in recent months, all
types of antiaircraft guns may be encountered. However, they usually are not numerous
and the crews are poorly trained. A less important but remote target frequently has
only medium and light antiaircraft guns. A new target under development and not
previously attacked may have no antiaircraft defense. The number and caliber of guns at
frequently bombed targets will, as a rule, be continually increased. Apparently the enemy
feels that such targets are strategically important to us because we bomb them often.
2. AT SEA
The size of Japanese sea-borne antiaircraft weapons generally is in proportion to the
size of the ships. Merchant ships of 5,000 or more tons frequently carry heavy
guns, while those between 3,000 and 5,000 tons usually carry medium guns. As a
rule, smaller merchant vessels are armed only with light weapons, but torpedo boats
and even smaller vessels usually mount medium guns, while heavy guns are always
found on destroyers and larger naval vessels.
In arranging antiaircraft weapons on ships, the Japanese concentrate the guns at the bow
and stern in order to obtain effective vertical (or near vertical) fire. Antiaircraft
machine guns and pom-pom guns are generally placed on the top bridge or near the bow
and stern. Light machine guns and rifles are placed around the front, back, and sides
of transports in order to "cover" dead space caused by equipment. Sandbags are used to
secure the tripods of the light antiaircraft weapons, and also to protect personnel
from hostile fire and sea waves.
Japanese ships usually execute sharp evasive movements, with frequent changes in course, when
attacked by aircraft. These tactics, the Japanese admit, lessen the accuracy of antiaircraft
The following notes were extracted from translations of Japanese documents dealing with
Air sentries and soldiers will report airplanes according to the direction of the clock, using
such expressions as "2 o'clock direction."
Open fire against hostile planes as soon as they come within effective range. Fire heavily, concentrating
on the most threatening targets, and seek to break up the hostile plan of attack before it
can be executed.
In firing at aircraft with rifles and light machine guns, it is essential to have a good
position. Rest your body and your left elbow on the gunwale and keep alert. Fire when the
ship is at the top or at the bottom of a wave. Get the bearing of the hostile planes, align
your sights, and then use following fire. If the hostile aircraft are over 2,000 feet
high, and if their cross-country speed is small, you will find it profitable to fire on
The following are the most important points in antiaircraft firing:
a. Do your best to judge the height of aircraft with your measuring instruments, and to
judge their course and speed with your naked eye.
b. Because of the pitching and rolling of the ship, the height-finder generally is
accurate only to within 4 to 5 degrees. If the pitching and rolling is considerable, special
adjustments are made, or corrections are made when the boat is level.
c. When attacked by a dive bomber, wait until the plane pulls out of its dive and then try
to shoot it down.
d. Against a torpedo bomber, it is necessary to open fire quickly and try to shoot it down
at a range of more than 1,000 yards.
Since the torpedo bombers fly low over the water as they come in to attack, fire shrapnel
at them with field artillery and mountain artillery guns which are distributed aboard
ship. A rapid rate of fire should be used.
To prevent hostile planes from strafing at low altitudes, small balloons should be raised
3. WHILE LANDING
The protection of landing coasts against air attacks is the responsibility not only of the
divisional antiaircraft dispositions, but also of each individual unit commander. In accordance
with this policy, the first-line units must form detachments for antiaircraft protection while
landing, and must prepare for air raids immediately after landing. These detachments and the
unloading units must dig the necessary protective trenches near the shore.
During landing operations, antiaircraft boats must be properly disposed, and part of the
antiaircraft artillery company must be landed immediately for shore protection.
When hostile planes dominate the skies, try to use the weapons attached to the large and the
small motor landing boats.
Boats which are not being used should be hidden immediately in the shade along the edge
of the water, or camouflaged with materials similar to the surroundings.
If boats in use are attacked, the formation and the direction of travel should be changed immediately.
To reduce damage from hostile bombs, transport ships should be anchored in an irregular
formation. Anchoring in a straight line would limit the field of fire of machine guns. As
a precaution against bomb damages, ships should be anchored some distance apart.
4. ON LAND
According to observers, Japanese land-based antiaircraft guns usually open fire while
United Nations planes are still out of range, and continue firing until our
aircraft are well away from the target. In most cases the fire is of the barrage
type, although a good deal of aimed fire has been encountered.
In one Southwest Pacific area, Japanese searchlights were slow in picking up planes—perhaps
because the planes approached in a glide. However, after picking the planes, the searchlight
crews held them well.
One crew observed two or three banks of searchlights. Each bank consisted of 12 searchlights, and
each acted as a unit. In the meantime, 15 or 20 other searchlights operated individually. Individual
searchlights were spaced at intervals of not more than 400 yards along the shore of
the defended area.