 It is a time of crisis. Men and material of the United States Army flow into the Republic of Vietnam. The build-up is rapid, for the modern army is characterized by speed and mobility. In the military world, exact numbers are never made common knowledge, but it is soon obvious that the population of American soldiers in Vietnam exceeds that of many American cities. The order to move out comes quickly and thus begins a process that is simply and accurately described as spreading out. Their destinations, while all within the borders of South Vietnam, will range from the capital city Saigon to the thinly populated mountain areas, the swampy Delta lands and the dense isolated jungle country. Soon, many thousands of men in units as large as the division, as small as the squad, are scattered over many thousands of square miles. And yet, it is vitally essential that a chain of command, a continuity of contact be established and maintained. It must be an unbroken, unbreakable chain, for to the soldier in the field, it will serve as a lifeline. This will be the story of that chain, an electronic achievement formally identified as United States Army Communications Vietnam. Today's globe spins within an invisible network built and maintained by the United States of America. It is our defense communication system, DCS, and it allows Washington and the Defense Department constant and immediate contact with armed forces installations all over the world. Strategic in nature, the DCS also overlaps into the tactical communications picture. And of primary importance today, of course, is its tie-in with military communications networks in South Vietnam. In Vietnam, military radio connections with the outside world, links to Bangkok, Okinawa, and the Philippines, are channeled through Army radio systems. These radio systems are located within the hub of all military communications in Vietnam, and that hub, very logically, is Saigon. These antenna towers, a short distance from downtown Saigon, pinpoint Phu Lam, the largest communications complex in the Republic of Vietnam. Its security maintained by both United States and Vietnamese troops, Phu Lam serves all major commands in the Saigon area. High frequency radios, each offering four voice frequency channels, maintain 24-hour contact with overseas and out-of-country stations. Three powerful transmitters, 8,000 watts to the Philippines, 10,000 watts to Bangkok, 30,000 watts to Okinawa, are part of Phu Lam's primary equipment, and additional transmitters stand by for backup. Saigon, the hub of all communications, is still only that, the hub, of equal importance, the wheel, in-country networks, both strategic and tactical, carrying vital telephone and teletype traffic. To create such networks, a terrain abundant with natural obstacles had to be electronically outwitted. To understand the unique communications problem faced in Vietnam, examine this profile view of some Vietnamese terrain, which very roughly approximates that between Saigon and Natrang. In conventional warfare, our forces might have advanced from point A to point B. Once at B, they would control everything behind them. Signal units could set up line of sight radios on mountaintops, and link the two points. But Vietnam is different. We might have units at points A and B, and yet not control the land between. Thus, line of sight radio equipment could not span A to B, because we could not secure that many sites without an excessive investment of men and material. The solution? Here. Signals bounced off the troposphere, by tropospheric scatter radio systems. These systems have greater range than line of sight equipment, and unlike high-frequency radio with its channel limitations, they can offer as many as 72 channels of communication. Long-range tropospheric scatter radio systems are vital components of the backbone network, the integrated wide-band communication system now shown on the map. Their space-spanning capability allows the system to net with Thailand. The backbone system is controlled by the Defense Communications Agency, and operated by the Regional Communications Group of the Strategic Communications Command's First Signal Brigade with the help of contractor technicians. And again, the Saigon area is the focal point. Here at Phu Lam, we can take a close look at one type of radio system used in the backbone network, the Mark 85. Housed in air-conditioned bands, it is officially a mobile tropospheric scatter radio terminal, and there are 85s in several Vietnamese cities. The radio is completely self-contained, with patching facilities, multiplexing components, receivers, transmitters, modulators, amplifiers, and generators. This particular system provides 72 channels of communication. The Mark 85 has two antennas, each a huge billboard, capable of receiving and transmitting. We are now approaching Bong Tao, southeast of Saigon, 30 minutes by air. Below is V.C. Hill, site of another station in the backbone system. Here, the continuing effort to expand army communications capabilities in Vietnam is visually evident. Bong Tao's impressive array of long-range radio equipment links it with Thailand, Saigon, and the logistically vital port of Cam Ranh Bay to the northeast. We are now inside a van, housing a Mark 98 tropospheric scatter radio system. Originally installed by the Air Force, this system, like some other elements of the backbone network, came under army operational control in mid-1966. This shift from Blue to OD gave Stratcom's first signal brigade, formed in April of 1966, to meet the obvious need for central control, responsibility for the bulk of the defense communications system in South Vietnam, along with all army tactical communications networks. Everything, in fact, but the equipment and nets organic to combat units. The 98's 10,000 watt output signals travel to the antennas along lengths of waveguide. The large parabolic dish antennas beam the signals and the many simultaneous channels of information they carry toward the distant stations. Supporting the backbone system and extending the worldwide communications chain toward the tactical level is this in-country network, consisting of medium-range tropospheric scatter radio systems and short-range microwave hops. The full network is not detailed on this map. But we can visit some of its stations and look at the equipment in use. We are now near Dalat, approaching Long Bien Mountain, site of a station in the medium-range network. Here, where nighttime temperatures can drop into the 30's, Track 90 radio systems are on 24-hour duty. Two of the radios offer 48 channels of communication with Play Koo and another maintains a 48-channel link with Saigon. The Track 90 circuits develop an extremely stable tropospheric signal, one that will not vary more than one cycle in 10 million. They can amplify a 50 millions of a watt signal to a full 1,000 watts. Long Bien Mountain, whose total channel capability will soon double, whose tie-ins with other stations will soon increase. From here, we go north. We are now within 100 miles of the 17th parallel, but still some 50 miles south of the northernmost station in the network. Here, within site of the South China Sea is Monkey Mountain, terminal for some of the network's short-range microwave hops. These antennas beam 10-watt signals on a line of site path. They point southwest toward identical units located in Da Nang. 45 channels are available between the two stations, and they are carried by Track 29 radio equipment, which has a maximum range of 30 kilometers. The Da Nang station also has Track 90 equipment, tying it to Chulai, Kuangai, and Wei, the northernmost station in the network. Links to Thailand, Okinawa, and the Philippines. Fixed long-range networks, extensions of the defense communications system, medium-range in-country networks, merging the strategic into the tactical, and the picture is still far from complete. To be added, an extensive array of supporting BHF tactical radio systems. These are mobile, flexible units, blanketing forward areas, ready to move and serve wherever our forces may be operating. One such is the Track 24, and a typical installation can be seen at Na Trang. It is at Na Trang that the trans-oceanic cable enters the country. The Trang station's relay all cable traffic to and from Saigon, and since the city is also the location of one of the two core-level tactical headquarters in Vietnam, it more than qualifies as another important communications hub. Reflector dipole antennas on 45-foot masks mark the location of the Track 24 systems. Shellders house the units, which offer line-of-sight communications over a maximum range of 40 miles. To operators of this smaller, lighter tactical equipment, a 100-degree temperature is the uncomfortable norm. Further into the field, closer to the infantryman, are families of even smaller radios. Forward Division tactical operation centers, some housed in air-delivered pods, include FM radios, transmitting the voice of command. Other communications devices are sheltered only by Canvas. Extremely mobile, they ride on trailers, or in the backs of Jeeps. Each is important, each is a link in the chain, a chain extending unbroken into the hands of the combat soldier. This is one of the Army's long-distance switchboards in Saigon. Their average volume, 15 to 17,000 calls per day. The Army telephone system in the Saigon area, larger than many serving some American cities, is growing daily. More sophisticated facilities and switchboards are constantly being installed. This style central office, for example, now serves U.S. Army headquarters in Saigon. Improvements far beyond the planning stage will soon multiply the number of telephone lines available and convert them to faster, more efficient, direct dialing. Teletype communications are equally sophisticated, 1200 words per minute. That is the speed at which this automatic multiple address and refile system cuts duplicate message tapes. This is a tape relay facility, one of the major installations of its kind in Vietnam. Completely modern in its equipment and methods of operation, it interconnects with other stations and relays to form a network that offers fast, efficient teletype services to the military. Data contained on cards, detailing requirements for men, money, and materiel, are transmitted with the speed and accuracy that only electronics can offer. The results, delivery of replacements, pay, and supplies to the critical place at the critical time. The contribution to combat effectiveness important today will be even greater tomorrow. In the future, approximately 20 data installations, processing cards at rates up to 200 per minute, will continue to ensure rapid response to the needs of our troops, as well as timely information to planners at all levels. This MSC-44 satellite tracking station adds still another dimension, another degree of sophistication. When it became operational in mid-1966, Saigon was provided with additional reserve ties to Hawaii and Thailand. And via Syncom 2, a direct connection with a major worldwide StratCom satellite communications base located in Asmara, Ethiopia. Communications, they must be established. They must also be maintained. What keeps this giant complex, the most sophisticated communications network that ever existed in a combat theater, operational, functional, on the air? The answer is people. The men in the technical control facility, receiving quick notification of circuit failure anywhere in the country, and contributing to the equally quick, responsive actions that follow. Specialists, technicians, doing tedious work under difficult conditions, and doing it well. Men with responsibilities ranging from the very simple adjustment to the very complex junction through which they must maintain a smooth, organized flow of traffic. They are all essential, all part of the total picture, whether they work in areas where the pressure is constant or in isolated sites where the greatest occupational hazard is monotony. Adding even further dimension to the integrated, wide-band communication system is the construction which is now in progress, and which will continue. With the help of the workers of several allied nations, the engineering and manufacturing skills of the American electronics industry, the officers and men of StratCom, the first signal brigade, and other signal units serving in Southeast Asia. United States Army Communications Vietnam will remain as modern, as reliable, and as sophisticated as is scientifically and humanly possible.