Military experience in World War II seemed to indicate that issuing a military compass to combat patrols in jungle terrain was beneficial to the soldier. As a result, the military even developed a water-filled compass that was able to function in hot and humid conditions. According to the Olive Drab, the military took a step backwards in Vietnam, when it purchased wrist compasses that were made by the Waltham Clock Co. These wrist compasses were not waterproof and did last long in the jungle.
As an interesting side light, U.S. armed forces fighting in New Guinea were able to successfully use small compasses that were built into match covers. These common items of the day were not official military gear, yet they still functioned in the New Guinea jungle, because they were waterproof. Also of note were some very sophisticated compasses issued to the U.S. Marines during Vietnam. Although better made than the previously-mentioned wrist compasses, these instruments also were not waterproof and suffered under jungle conditions.
Navy sea and air patrols were often issued a small survival compass known as the MC-1. This item was 2 inches in diameter and was often built into life jackets and other survival gear. The rudimentary compass was designed to be used as a sighting device along with its ability to register magnetic north and break down compass bearings into 30 degree intervals. All written material seems to indicate that these basic instruments worked and functioned, as long as the user was not located next to a large metal object, which would affect the magnetic north reading.
A gyro compass is a non-magnetic compass that is used as navigational equipment on many types of military boats and warships, including submarines. Gyro compasses run off electricity and have several advantages over magnetic compasses. First of all, they register true north and are not affected by large metallic structures. Also, gyro compasses are extremely accurate and do not use a long needle. However, since they run off electricity the compass is subject to electrical failure. As a result, magnetic compasses are always present in case a backup is needed.
