The Japanese armed forces developed, both before and during the war, a fairly extensive line of hand and rifle grenades. This type of ordnance, primarly used by ground forces, was developed by the Army, but in the peculiar Japanese military organization, was also used by the Navy ground defense units.

The hand and rifle grenades used by the Japanese, although designed for a large variety of purpose, are similar is a number of respects. Generally, they are similar than would be considered adequate by American standards. Also, observation ot them in use has shown that, although explosive charges are usually large enough, effective fragmentation is of-ten not achieved. In the main, the missiles are lacking in safety factors, and in reliability, the principles used in the igniters being of such character that they may be initiated ac-cidentally and are subject to deterioration because of exposure to moisture. In the case of grenades of glass construction, the danger of initiation is great.

Rifle grenades are often standard hand grenades, adapted for use as rifle grenades by the addition of a tail portion. Hand grenade igniters are retained, with delay trains remo-ved in some cases.

A large variety of improvised grenades has been found in all Pacific areas. These grena-des have been adapted from such items as small ammunition, small bombs, pipe, paper, and wood. In general improvisations were the result of shortage of the manufactured item, and were prepared by inexperienced personnel. Consequently, they were, in almost all cases, very ineffective and extremly dangerous to use.