The AN/MPQ-14 is a radar system used for Ground Directed Bombing (GDB), where a plane is remotely piloted from the ground with radar assistance, up to and including the point of bomb release. It was the first guided weapon system used by the U.S. Marine Corps, and introduced the ability to deliver ordnance in close air support missions in poor visibility conditions.. Initially developed as a training substitute for a guided, submarine-launched weapon, its creaters realized it had potential as a night/all-weather bomb delivery system. It saw service in the Korean War, and its successor, the AN/TPQ-10, was used in Vietnam.
Dalby, MSgt. William L. Holtz and MSgt Floyd A. Dickover, were brought into the Loon project by Cmdr. Grayson Merrill, who envisioned advance teams of Marines, landed by submarine, providing terminal guidance from greater proximity to the target. Since there were too few Loons to regularly test-fire and it was too difficult to arrange for a submarine and other logistical preparations, the Marines got only two test-firings with their improvised equipment. As a result, MSgt. Clark. D Hayden concocted a device that would simulate the Loon — in the controlled part of flight, the Loon would be simulated by a fighter whose automatic pilot received radio commands as the Loon would. Ground radar tracked the plane, an improvised computer generated control instructions for the plane to maneuver and signaled the pilot to drop the bomb at the right time. The system worked effectively and had an accuracy measured in yards, not miles as with the Loon.
Inspiration struck when Dalby and Cpt. Samuel A. Dressin, simultaneously hit upon the idea of using the system as a weapon in its own right — a radar-guided bomb sight for night or bad weather. They redesigned the system to be hardier for battlefield usage, moving from the initial SCR-584 radar to the SCR 784, developed for Army antiaircraft artillery.
The system was demonstrated at MCB Pendelton in 1950 to a group of ground and air Marines. In the brief, Cpt. Dalby claimed a CEP of 150 yards for a weapon dropped from 18,000 feet, with complete guidance from the ground. The demonstration was successful and won supporters in the Marine Corps. Dalby had the unfortunate experience of letting a brigadier general examine the equipment, spurring the comment that "rain would short out this maze of wires in nothing flat". Dalby later declared he would "never let a general behind the scenes again until I have it packaged up like a box of candy."
The system was designated AN/MPQ-14, and with the aid of Lt. Col. Homer G. Hutchinson, the project received support from Washington, including two Corsair night-fighter aircraft and pilots for training. Dalby described Hutchinson, an aviator, as an officer who "really knew his way around the whole Washington jungle... Without Hutchinson's help, the whole MPQ-15 project would probably have died".
The setup was ready to see combat in July 1951, and Colonel Victor H. Krulak, then chief of staff of the 1st Marine Division, urged its immediate deployment. Krulak had been one of the Marines to witness its first demonstration at Pendelton in 1950. The commander of the 1st Marine Air Wing placed it with the 1st Marine Division near the 38th Parallel. It won many fans on both the ground and air sides. The 1st MAW's Corsair night-fighter squadron, VMF-513, were especially enamored with the device as it allowed them to fly at 15,000-20,000 feet, above anti-aircraft fire, rather than low in the valleys to try to use flares to locate targets. Though initially only cleared for use within a mile of friendly forces, by summer 1952 the Marines had obtained permission from the Fifth Air Force to use it in a CAS role.
In Vietnam, its successor, the AN/TPQ-10 was used with great success, especially at Khe Sanh, where poor weather made conventional CAS methods unreliable. The AN/TPQ-10 had a 50 yard CEP and could handle up to 105 missions a day. The commander of the Khe Sanh defense, Col. David M. Lownds, said "Anything but the highest praise would not have been enough."