The following WWII report on Japanese obstacles was originally published in Tactical and Technical Trends, No. 10, Oct. 22, 1942. [DISCLAIMER: The following text is taken from the U.S. War Department publication Tactical and Technical Trends. As with all wartime intelligence information, data may be incomplete or inaccurate. No attempt has been made to update or correct the text. Any views or opinions expressed do not necessarily represent those of the website.]

JAPANESE DOCTRINE ON OBSTACLES The following is a summary of a translation of portions of the Japanese Field Fortification Manual: a. Electrical Obstacles (1) Principle Electrified wire is used to cause casualties to men and horses and to hamper hostile attacks. (2) Construction 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 are given.) (3) Use 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 (1) Types 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.

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