Japanese Navy bombs are divided into classes: land bombs, ordinary bombs, special bombs, smoke bombs, practice bombs, target-marker bombs, training bombs, and dummy bombs.

"Land" bombs are bombs specially designed for use against land targets. They are usually of rough construction.

"Ordinary" bombs are designed for use against ships. They include both G.P. and S.A.P. types. They are smoother construction than land bombs.

Special bombs are designed for various special purpose and each special class is indica-ted by a mark number. (See color chart.)

According to a captured document a new system of designating Navy bombs has been proposed. The existing bombs are not to be redesignated but new bombs will be assigned mark numbers as follows:

Marks 1 through 9, antishipping bombs.

Marks 10 through 19, chemically equipped bombs.

Marks 20 through 29, antiaircraft bombs.

Marks 30 through 39, antiland bombs.

As the name indicates practice bombs are used for practice bombing. Targetmarker bombs are used as target marking beacons.

Dummy bombs are used for training and practice bombing. Training bombs are used for training in handling bombs.

Smoke bombs are used for concealment purposes.

Individual bombs in these main general classes are given further designations.

a. The type number discloses the year that the bomb was adopted for service use.

In the "land" and "ordinary" bomb classes, the first bomb of a given weight class is not assigned a type number but is merely indicated by the weight number. Subsequent de-signs of the same weight are assigned type numbers. Thus there is a No. 6 land use bomb and a type 97 No. 6 land use bomb.

b. The number indicates the weight of the bomb in units of tens of kilograms. Thus a No. 6 bomb weighs 60 kg., a. No. 25 bomb weighs 250 kg, etc. This designation is as much an indication of size as it is weight, No. 6 indicating a bomb of the 60 kg. size, and ap-proximate weight.

c. A description of the bomb is indicated by the character for land use, ordinary, etc. It if is a special bomb, the mark number is given.

d. Model: This term has serverak meanings but in this instance is used to distiguish diffe-rent designs of bombs in the same general class.

e. Modification: This term represents a minor change in design or a change is filling.

There are two main patterns of construction of Navy bombs, typified by the "land" bombs and the "ordinary" bombs.

a. Land bombs: Land bombs are of three-piece construction. The nose is attached to the cylindrical body either by welding and riventing or by welding alone. The tail cone, which is filled with explosive is attached to the body by means of a collar or coupling ring. Either the body or tail cone is attached to the collar by welds and/or rivets and the final junction is made by attaching the other part to the collar by screws.

b. Ordinary bombs: Ordinary bombs are of two-piece construction. The nose and body are manufactured of one piece, and are machined both inside and out. If the tail cone is filed it is threaded into the body or in the case of larger bombs an interrupted screw ar-rangement is used to attach it to the body. If the tail cone is empty a male base plate closes the after end of the body and the cone is attached to the base plate by threads or screws.

The construction of special bombs and other general classes varies greatly and is cove-red in the description of each individual bomb.

Bombs up to and including 250 kg. are suspended by a single U-shaped fixed lug. Two lugs 180° apart may be fitted to the bomb. Larger bombs may by suspended from a tor-pedo-release gear by two flat guide studs located 180° apart or by a suspension band fitted with the standard lug.

Navy bombs are generally filled by casting the explosive directly into the case. The ca-vity is protected by a thick coat of laquer. In some instances the explosive may be per-formed into paper-wrapped sections which are usually additionally protected by a wax or a flannel coating.

During the war the Japanese Navy has modified the color system used to differentiate its bombs. Under both the new and old systems, the basic body color is grey; this color va-ries from greenish-grey to bluish-grey depending on variations in the paint and weather-ing conditions. This grey paint is applied over a red anti-corrosive paint.

The old color pattern consisted of painting key colors as a broad band on the nose and tail struts. Usually these colors were the same. A band slightly aft of the suspension lug was additional key. Thin red stripes 180° apart running from nose to apex of tail cone appeared on all service bombs.

In the new scheme all bombs containing explosive have the nose tipped in green. Key color bands appear aft of the green tip and an additional key color band may appear on the tail strut. The red stripes have been dropped. Colored body bands are used in some instances to indicate different modifications. (See color chart.)

As a rule Navy bombs of 250 kg. and larger in weight are fitted with fuze pockets in both nose and tail. The No. 6 and No. 3 size of land use and ordinary bombs have nose poc-kets only.