The theory of air-borne attack presupposes assault upon a hostile area under conditions wherein the only link with the higher command is through means of communication carried with the attacking troops or improvised by them. Portable radio sets constitute the basic means of establishing contact with other units, with headquarters, and with the friendly aircraft operating in the area. Because of the likelihood of heavy casualties during the early phases of the attack, assault units are provided with about twice the amount of radio equipment ordinarily assigned to ground combat units of the same size. A parachute rifle battalion appears to be equipped with two radio subsections for battalion-to-regiment communication, and eight very high-frequency radio subsections for point-to-point communication on the general company-to-company circuit.

a. Types of Radios

German air-borne attack troops, during the operations at Crete, were equipped with several types of radios, but two types were most extensively used. The pack "b.1," which was carried in three parts, weighed about 120 pounds all told. Operating on a frequency of 3,000 to 5,000 kilocycles, the "b.1" transmitter had a range of from 10 to 15 miles. The pack "d.2" (very high frequency) weighed about 40 pounds and had a range of 7 1/2 to 10 miles. This model operated on 33,800 to 38,000 kilocycles. Both of these sets, being very light, are well suited for use by air-borne units.

b. Visual Communication

Ground-to-air visual communication is accomplished by a variety of means: by flags, by colored smoke signals, and by panels. During the Crete operations, swastika flags were used to denote German troops. White or yellow ground panels of cloth were used to indicate front lines. Headquarters positions were indicated by panels in the form of a cross, and spots where supplies were to be dropped by two "X's", side by side. Direction of resistance was indicated by inverted "V's" with the point in the direction of the resistance. Various other panel designs were similarly employed to convey prearranged messages. Green smoke signals were used to attract the attention of aircraft where supplies were wanted. Red smoke signals are also believed to have been used, to indicate enemy defended positions. In Crete some British learned the German panel calls and used them to send for reinforcements (whom they shot), for food (which they gladly ate), and for other supplies.