United States Army Signal Corps
The U.S. Army Signal Corps was in a part of the United States Army founded in 1861 by Major Albert J. Myer, a physician by training. The Signal Corps develops and tests communication equipment for the battlefield
World War II
The term, RADAR, was first coined by the Navy in 1941 and agreed to by the Army in 1942. The definition given in the first Signal Corps Field Manual on Aircraft Warning Service stated, "RADAR is a term used to designate radio sets SCR (Signal Corps Radio)-268 and SCR-270 and similar equipment".
The facts were that the SCR-268 and 270 were not radios at all, but for top security] reasons were designated as such. Although important offensive applications have since been developed, radar emerged historically from the defensive need to counter the possibility of massive aerial bombardment.
In 1941 the laboratories at Fort Monmouth developed the SCR-510. This was the first FM backpack radio. This development was an early pioneer in frequency modulation circuits, providing front line troops with reliable, static free communications. They also fielded multichannel FM radio relay sets (e.g., AN/TRC-1) in the European Theater of Operations as early as 1943. FM radio relay and RADAR–both products of the Labs at Fort Monmouth, are typically rated among the four of five “weaponsystems” that made a difference in World War II.
In December 1942, the laboratories had personnel strength of 14,518 military and civilian personnel.The Signal Corps Ground Service was directed by the War Department, however, to cut the total military and civilian personnel to 8,879 by August 1943. In June 1944, “Signees”, former Italian prisoners of war, arrived at Fort Monmouth to perform housekeeping duties. A Lieutenant Colonel and 500 enlisted men became hospital, mess, and repair shop attendants, relieving American soldiers from these duties. Also in December 1942, the War Department directed the Signal Corps General Development Laboratories and the Camp Evans Signal Lab to combine into the Signal Corps Ground Service (SCGS) with head-quarters at Bradley Beach, New Jersey (Hotel Grossman).
Julius Rosenberg worked for the Signal Corps Labs from 1940 to 1945. He was dismissed early in 1945 when it was learned he had been a member of the CPUSA secret appartus, and had passed to the Union of Soviet Socialist Republics the secret of the proximity fuse.
The Signal Corps' Project Diana, on 10 January 1946, bounced radar signals off the moon.
In 1948 researchers at Fort Monmouth grew the first synthetically produced large quartz crystals. The crystals were able to be used in the manufacture of electronic components, and made the U.S.largely independent of foreign imports for this critical mineral. In 1949 the first auto-assembly of printed circuits was invented. A technique for assembling electronic parts on a printed circuit board, developed by Fort Monmouth engineers, pioneered the development and fabrication of miniature circuits for both military and civilian use. Although they did not invent the transistor, Fort Monmouth scientists were among the first to recognize its importance, particularly in military applications, and did pioneer significant improvements in its composition and production.
Everything was to change as world tensions increased with the Cold War and the Berlin Airlift. To sustain the Army's worldwide commitments, it again became necessary to enlarge the capacity of every activity on Post.
In June 1950, with the onset of the Korean War, President Truman quickly received the necessary authorization to call the National Guard and organized reserves to 21 months of active duty. He also signed a bill extending the Selective Service Act until 9 July 1951. The Officer Candidate School was reestablished.
The fighting in Korea brought to light the need for new techniques in the conduct of modern warfare. The use of mortars by the enemy, and the resultant need to quickly locate and destroy the mortar sites resulted in development of the Mortar-Radar Locator AN/MPQ-3 and AN/MPQ-10. The Communiations Electronics Research and Development Engineering Center, better known as the Albert J. Myer Center, or simply, the Hexagon.
The development of new equipment, however, placed requirements on the Signal Corps to provide increased numbers of trained electronics personnel to work in the fire control and guided missiles firing battery systems. To meet this need, Signal Corps Training Units—the 9614th and 9615th—were established at Aberdeen, Maryland and Redstone Arsenal in Alabama. These units provided instructionon electronics equipment used in the Anti-Aircraft Artillery and Guided Missile firing systems.
Following the arrest of the Julius and Ethel Rosenberg in 1950, two former Fort Monmouth scientists, Joel Barr and Alfred Sarant, defected to the Soviet Union. On 31 August 1953, having received word of possible subversive activities from Fort Monmouth’s commanding general, Kirke B. Lawton, the Chairman of the Permanent Subcommittee on Investigations (PSI), Senator Joseph McCarthy, suspected a spy ring still existed in the Signal Corps labs. At first, McCarthy conducted his hearings behind closed doors, but opened them to the public on 24 November 1953. Extensive Congressional Hearings were continued in 1955 under the chairmanship of Senator John McClellan of Arkansas.
McCarthy’s 1953 investigation into the United States Army Signal Corps Center at Fort Monmouth, New Jersey, was prompted by a defecting East German Scientist’s claim of having seen microfilmed documents from that center.”  An investigation had led officials to the conclusion that he was unreliable, but Senator McCarthy’s subcommittee still began holding hearings on the case, suspending, among others, researcher Aaron H. Coleman. Coleman had been suspended in 1946 for not keeping classified documents he’d taken home in a safe with a three combination lock. Army officials had determined that the documents, which were of little importance, had been used for personal study rather than any attempt at passing on information, but McCarthy declared that Coleman, who was guilty of having been a college classmate of Julius Rosenberg, “may have been the direct link between the laboratories and the Rosenberg Spy Ring. 
The Army averred that no documents were missing and its own investigation had found no evidence of a spy ring, maintaining that what the defecting scientist had seen had probably been Signal Corp data that had been shared with the Russians during the War under Lend Lease. Still, the investigation went on. When electrical engineer Carl Greenblum, whose mother had died two days before, broke down and wept during Roy Cohn’s cross-examination and had to be led, visibly upset, from the closed door session, McCarthy announced to the press that “I have just received word that the witness admits he was lying the first time and now wants to tell the truth.” Greenblum’s name was leaked to the press and he and his family were harassed, a hammer and sickle painted on the door of their home. Greenblum explained that after he’d broken down he’d “sent word that I wanted to go back and tell my story from the beginning. That may have been interpreted to mean I was lying but that certainly was not the case.” Greenblum was fired from his job, but reinstated in 1958. 
The fifteen hearings resulted in no indictments of any individuals, and established only that a few Communists had worked at Fort Monmouth from 1941 to 1947 – something that was already known by the Army -- and there had been a small communist cell at one of their subcontractors in Nutley New Jersey. There was no substantive evidence to connect these groups or individuals to espionage. 
- McCarthy Hearings 1952-54, Vol 1.
- The Life and Times of Joe McCarthy: A Biography, Thomas C. Reeves Pg. 521
- ”McCarthy Hearings, Volume 3, files.findlaw.com/news.findlaw.com/hdocs/docs/mccarthy/hearingsvol3.pdf."
- Army Signal Corps—Subversion and Espionage, October 22 (PDF). Executive Sessions Of The Senate Permanent Subcommittee On Investigations Of The Committee On Government Operations; Vol. 3. pgs. 2717-2726, U.S. Government Printing Office (1953)., Haynes & Klehr. Venona: Decoding Soviet Espionage in America. ISBN 0-300-08462-5. )
- “McCarthy Hearings 1952-54, Vol 1.