The following is a summary of a translation of portions of the Japanese Field Fortification Manual:
a. Electrical Obstacles
Electrified wire is used to cause casualties to men and horses and to hamper hostile attacks.
Normally, wire is strung on dry poles with bark removed, or on poles with all buried
portions insulated with asphalt or coal tar. The bare wire is strung and connected
with a high-tension source (1,000 to 2,000 volts AC), so that a person coming in
contact with the obstacle wire closes the circuit. Transmission wires may also be
strung along the ground, or under ground. (No details of the generating plant
Ordinarily, the current is not turned on except during actual attacks. A variation
consists in electrifying certain sections of the wire during hostile reconnaissance, and
electrifying additional sections during the attack.
(4) Reconnaissance of Hostile Electric Obstacles
The Japanese consider it important to locate electrical obstacles prior to an
attack. Reconnaissance parties attempt to determine the characteristics of the
source of power, and of the transmission lines. The following points are
indicative of the presence of electrified obstacles:
Bark stripped off lower portions of wire obstacle poles.
Presence of asphalt cloth or other insulation around the buried portions of posts and pegs.
Any noticeable decrease in the number of wires, posts, and pegs.
Low wires free from contact with the ground.
Absence of additional loose barbed wire (used in some cases to strengthen obstacles).
Presence of insulators or transmission wires.
Burnt or smoldering grass close to wire lines.
Sparks when small-arms fire cuts the wire.
(5) Use of Detectors
The Japanese use several types of electrical detectors. One appears to be a simple
voltmeter. Another type is a field telephone to pick up earth currents resulting
from electric wire at distances of over 100 feet. Also mentioned are a magnetic
induction detector with a range up to 1,300 yards, and an improvised detector
using a radio receiver amplifier with a range up to 500 yards.
(6) Destruction of Electrical Obstacles
Destruction is accomplished by demolition, wire cutting, and artillery fire. In
some cases lines may be shorted by throwing water or brine on the posts. Bangalore
torpedoes are the best means of demolition. After the use of both demolitions and
artillery fire, loose wire ends are dangerous and must be avoided. Special squads
equipped with rubber gloves, rubber boots, wire-cutters, and some
type of nets for cutting paths through wire are trained in following up demolition
work. No matter what the method of demolition, it is emphasized that a path
wide enough for the passage of the attackers must be created, and all loose wire
ends must be wrapped around posts. The resulting paths should be clearly marked.
b. Mines and Traps
(1) Mine Detection
The Japanese emphasize the necessity for studying the functioning of enemy mines and the
enemy procedure for mine laying. Mine detection is generally a mission of technical troops.
(2) Elements of Detection
A detailed search for enemy mines should include attention to the following:
Those regions from which the enemy purposely keeps away.
Presence or absence of sentries.
Removal of civilians.
Intelligence re enemy's mine laying.
Change in color of soil, small swells, and mud cracks.
Exposures or traces of plates, wire, etc.
Any trip wire and rope on ground, or roads, or in forests.
Presence of poles and pegs whose use is unusual.
Waste paper or packing bits used in mine laying.
Mechanical noise coming from clock-run delay device.
Smell of chemical from chemical delay device.
Connection wire between obstacle and ground.
Wire connecting abandoned weapons and other booby traps.
Rocks scattered on roads.
Wire fastened to doors and windows.
(3) Probing Rods
A mine-detecting rod for probing is mentioned. Lacking other means, spades are employed.
(4) Mine Destruction
The Japanese prefer to remove discovered mines, but on occasion will mark located
mine fields or will destroy mines by firing them.
c. Antitank Obstacles
The Japanese recommend use of the triangular trench, circular pit, and side-hill
barriers for antitank defense. In the use of portable obstacles, two
tows on level ground and single rows on steep slopes are suggested.
(2) Destruction of Obstacles
The destruction of steel-rail obstacles and side-hill barriers by explosives is
recommended. It is suggested that generally it is best to fill trench-and-pit-type
obstacles, using crib-work and earth-filled baskets.
Comment: It is recognized that this particular Japanese text deals with
obstacles in a very superficial manner. This summary is presented in order to
give a Japanese approach to the obstacle problem. Nothing has occurred in the
war thus far to indicate a general Japanese weakness in dealing with mines or obstacles.