Japanese land-mine technique has reached its highest point to date in the
efforts of the enemy to lay mines on beaches as a defense against
probable U.S. landing operations.
Recent island assaults in the Central Pacific have disclosed a trend toward
antiboat and antivehicle beach-mining, a type of activity which may be encountered
to an even greater extent in the future. Until now this defensive tactic has been
met principally on comparatively small islands where suitable landing
beaches have been limited, and where the Japanese have had ample time to
construct strong defensive installations.
The mine most frequently encountered in beach areas has been the double-horn
hemisphere mine. The detonators of this mine consist of two lead-alloy horns, each
containing a vial of acid. When either horn is bent or crushed, the acid vial is
broken. The acid then contacts battery plates and generates a current which
detonates the mine.
This mine has been used by the Japanese in several ways. Usually the mines
have been set so they would detonate when pressure was put upon trip wires
connected to the detonating horns.
At Tarawa this mine was found emplaced in the shallow water off shore. They
were set between posts and other antiboat obstacles, and trip wires were
strung from the horns to the top of each adjoining obstacle.
During the landing on Tinian Island, hemisphere mines were found buried on
the beach between the high and low water lines. In this position they were
a hazard to boats beaching at high tide, and to personnel wading ashore from
boats at low tide.
On other beaches many mines were found buried to horn depth in the sand and
connected by trip wires strung between the horns of two or more mines. When
wired in this manner, the weapons serve as antipersonnel as well as antivehicle
Although these mines have been developed and used principally as an antiboat
mine, it is not uncommon to find them emplaced several rows in depth on beaches
and in the area just to the rear of the beach. When laid in this manner, they
usually are set with a trip wire between mines, and constitute a hazard
both to troops and to vehicles moving inland from the beaches.
To date the Japanese have tended to concentrate their efforts at mining to the
beaches, and have neglected to use efficient inland minefields. This might be
attributed to the characteristic Japanese defense doctrine which provides for
the defeat of their enemies "at the water's edge," and does not envisage the
possibility of an inland battle after a beachhead has been seized by the