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90 MM GUNS (22 K)

Totally in the Dark? A Beginner's Guide
to the Skylighters, WW II Antiaircraft
Artillery, Searchlights, and Radar

Who Were the Skylighters?
   The Skylighters were the 800-odd men of the four batteries of the 225th AAA Searchlight Battalion. After training at Camp Davis, North Carolina, the 225th arrived in England just before New Year's Day 1944, and became part of the antiaircraft defense of England. In mid-June, the Skylighters landed on Omaha Beach and formed part of the defense of Normandy. Thereafter, for most of their dash across France and the Low Countries, the 225th were attached to the 9th Air Force's 422nd and 425th Night Fighter Squadrons, who flew the deadly P-61 Black Widow interceptor against the Luftwaffe. In their role with the night fighters, the 225th received partial credits on the downing of 36 enemy planes and V-1 buzz bombs. In addition, the battalion's 36 General Electric searchlights were used to put up over 4,000 light canopies that saved countless planes as well as pilots and aircrews that were lost or disabled in night combat in the ETO. Skylighters radar sets were used to vector the Black Widows to their targets time and time again. At war's end, the 225th began training for deployment to the Pacific, and served for a while as part of the Army of Occupation. Following the surrender of Japan, Skylighters began rotating back home, and by December 1945 the unit was disbanded.

   We recommend you begin with our Unit History to start your exploration of this site, and read our Mission Statement and Dedication to understand why we built this site. In a few words, it exists to commemorate the war experiences of those who've gone and those who remain, both in the 225th and in the armed services at large, 1941-45. A poet once said: "They shall grow not old, as we that are left grow old; age shall not weary them, nor the years condemn. At the going down of the sun and in the morning, we will remember them." This is an act of remembering the men of the 225th, and their brothers in arms, as they were, all those years ago.

   Although this site is a massive work in progress, our motto is "information kept secret is lost." With WW II veterans dying at the rate of 1,000 a day, there is no point holding the information back. Many sections of this site are very much works in progress, but we hope this state of "constant evolution" induces visitors to return to see what's new, what's changed, and what's been added to previously launched features. What is currently available should help to increase your knowledge about the Skylighters, AAA units, and World War II in general.

Postcard depicting training with Sperry AAA searchlights at Camp Davis, 1943
(click on the photo to view an enlargement).

What Does AAA Mean?
   AAA means Anti-Aircraft Artillery. You can pronounce it "Triple-A", as in "225th Triple-A Searchlight Battalion."

What Was the Coast Artillery?
   The Coast Artillery was the branch of service from which most of World War II's antiaircraft battalions were constituted. The 225th, for example, can trace its "lineage" to the 3rd Battalion of the 510th Coast Artillery Regiment.

   The concept of seacoast defense became extremely important in the United States after its severe lack of preparedness during the War of 1812. This emphasis continued after the Civil War as more powerful and more sophisticated artillery weapons were developed. As the 20th Century approached, military strategists realized that heavy (fixed) artillery required a very different training program than lighter, mobile field artillery. The obvious solution was to divide the Artillery Corps into two new branches: Field Artillery and Coast Artillery. This process began in February 1901 with the creation of dozens of Coast Artillery companies. Six years later the venerable Artillery School at Fort Monroe became the Coast Artillery School. It operated at this post until 1946, serving as the principal training center for most officers and many enlisted men in this branch of the Army.

   During the 1880s a special board convened by Secretary of War William Endicott made sweeping recommendations for new or upgraded coastal defense installations and weapons systems. The primary artillery pieces were the 12-inch mortar and the "disappearing" gun (available in at least five sizes), supplemented by smaller armament. Foreign navies eventually developed new guns that exceeded the range of these weapons, so the Coast Artillery responded with 16-inch howitzers and guns. During World War I thousands of Coast Artillerymen received abbreviated training at Fort Monroe and other training centers before going overseas to serve in railway or field artillery batteries.


   By World War II the Coast Artillery Corps had shifted its emphasis to antiaircraft artillery (AAA), and units with original Coast Artillery designations, like the 225th, were reorganized as AAA units.

Men of the 246th Coastal Artillery stationed at Fort Story, Virginia add a personal touch to their 16-inch shells.
Image reproduced courtesy of Fielding Tyler/Coast Guard Museum.

The older, larger guns at seacoast installations were retained for training purposes but were practically useless against long-range bombers or carrier-based aircraft. Even before the war ended, the U.S. Army began to phase out its coastal defense operations and divert manpower to higher-priority needs. In 1946 the Coast Artillery School moved to Fort Winfield Scott, California, as military experts pondered the fate of this Corps. Not unexpectedly, the Coast Artillery Corps was inactivated on January 1, 1950, in accordance with the Army’s latest reorganization plan.

What is Antiaircraft Artillery?
   Antiaircraft Artillery is the branch of the U. S. Army dedicated to protecting ground forces and other static elements (aircraft on airfields, harbors, etc.) from concentrated aerial attack. The phrase "ack-ack" is derived from antiaircraft, so many AAA units were known as ack-ack outfits. The word "flak," from the German term Fliegerabwehrkanone, or aircraft-defense gun, refers to either the artillery or the bursting shells fired from AAA guns. More information about AAA in World War II is available here.

   At the beginning of World War II the U. S. antiaircraft artillery force was very much the poor stepchild of the Coast Artillery Corps. The units were mostly three-battalion (a gun battalion, an automatic weapons battalion, and a searchlight battalion) regiments and separate battalions. They were equipped with a motley mix of obsolescent 3-inch guns and single-barrel, water-cooled .50-caliber machine guns. The German Blitzkrieg in Europe forced a widespread reevaluation of the Army's AAA capability and, beginning in 1940-1941 a vast expansion of the arm (it finally achieved an identity separate from the Coast Artillery in 1943). On 30 September 1942, it was proposed that 811 AAA battalions be organized (with a total strength of 619,000 men).

   However, this massive buildup of AAA units became largely redundant when another formerly poor relation of the U. S. Army, the Army Air Corps, wrested command of the air from the Luftwaffe in 1943 and 1944. Many AAA battalions were disbanded to provide replacements in 1944, and some were converted to field artillery. A total of 258 battalions were inactivated or disbanded between 1 January 1944 and 8 May 1945. Nevertheless, the AAA remained a strong component of the army and achieved something of resurgence in late 1944 in Belgium, defending Antwerp from the threat of the V-1 "buzz bombs." On 31 December 1944, there was still a total of 347 AAA battalions (with 257,000 men) active in the Army.

   In 1943 the AAA regiments were broken up into separate battalions, with the regimental H&H companies becoming new AAA Group Headquarters. The AAA battalions were organized as either gun (equipped with the M1 90mm AA gun) or automatic weapons (equipped initially with a U.S.-designed M1 37mm gun, but later almost wholly re-equipped with the famous M1 40mm Bofors-designed gun, and with the M51 or M55 quad-mount .50-caliber machine gun). Battalions were further classified as mobile (that is towed), SP (self-propelled, utilizing halftrack-mounted guns, the M16, a quad .50-caliber mounting, and the M15, a combination mounting twin water-cooled .50 caliber and a single 37mm), or semimobile (with a reduced number of prime movers, designed for the defense of static installations).

   The automatic weapons battalions of all types were organized with four firing batteries, lettered A to D, an H&H Battery, and a Service Battery. Each battery nominally contained eight towed 40mm or 37mm SP guns and eight quad .50-caliber towed or SP machine guns. However, many slight variations existed, some battalions had batteries composed of eight towed 40mm guns, four quad .50-caliber mounts, and eight single, water-cooled .50 caliber machine guns (there was a shortfall in production of the M51 and M55 mounts). Gun battalions were organized identically, except the batteries were equipped with four 90mm guns each and, usually, three water-cooled .50 caliber machine guns.

Tools of the trade for the "Moonlight Cavalry," aka searchlight units.

   Normally, an AAA automatic weapons battalion was attached to each division, SP if attached to an armored division, and mobile if attached to an infantry division. A corps normally had one or more AAA groups attached. Each AAA group consisted of two or more automatic weapons battalions (usually mobile), although a gun battalion was occasionally attached. In the European Theater, gun battalions were more frequently found in AAA groups attached to the army or army group. Antiaircraft brigades were also formed and were normally attached to armies or to theater commands. In addition, the IX Air Defense Command (in effect an AAA division, originally organized as a part of the US Ninth Tactical Air Force), with an average of ten to fifteen gun and automatic weapons battalions, formed a powerful AAA reserve for the US 12th Army Group in Europe.

LIGHTS IN ACTION   Searchlight battalions (dubbed the "Moonlight Cavalry" by their colleagues in the AAA business) generally consisted of about 800 men and 36 searchlights divided among four batteries (HQ, A, B, and C). Each battery A – C had 12 lights divided among three sections (four lights per section). While both lights manufactured by Sperry Gyroscope and General Electric were deployed in WW II, all of the 225th's lights and power plants were GEs. In addition, many were outfitted with gun-laying radar sets, notably the SCR-268 and SCR-584 units (the 225th used both). At the time, these radar sets were top-secret. The main AAA weapons of a searchlight battalion were .50-caliber machine guns, mounted either singly on tripods or in fours on a gun carriage ("quad fifties"). The 225th was a semi-mobile battalion, meaning that part of its equipment was towed, i.e., searchlights, trailers, generators, radar sets, etc. The line drawing above shows the "tools of the trade" for a searchlight battalion. Clockwise from the upper left: SCR-268 gun-laying radar set, deuce-and-a-half prime mover, searchlight power plant, and .50-caliber AAA machine gun. In the center, the searchlight itself.

   AAA training was done all over the country, but Camp Davis, North Carolina, where the 225th trained during the Summer of 1943, was the location of the Army's AAA training center. Two USAAF towing squadrons based at the camp's airfield provided aircraft that flew thousands of miles each week — both day and night — in missions along the coast. At night the planes gave the 225th and other S/L battalions practice in picking up enemy raiders in the dark, a job that they would have to do for real once in England and later on the Continent.

You have searchlight-aided night firing, so you could pick out the sleeves, and tracers arch out over the ocean. It was sort of a beautiful sight. In fact, I got married while I was home on furlough. My wife came down and lived at Carolina Beach for several months, just before we were alerted for shipment overseas . . . Now they could sit down on Carolina Beach and watch the 40s and 50s being shot out over the ocean. It was a really beautiful sight.
— Staff Sgt. Herman Ledger
599th AAA (AW) Battalion, (C Battery)

AAA overview text Copyright © 2000 Rich Anderson, via Military History Online, except for description of S/L battalions.

LEFT: The Dec. 1941 of Popular Science depicts a Coast Artillery sound locator (compare this late 1930s model to the WW I version below). RIGHT: The Apr. 1941 issue of Popular Mechanics shows an AAA man at the binocular sighting system for the 60-inch searchlight behind him.

How Did AAA Units Operate?
   Normally, an AAA automatic weapons (AW) battalion was attached to each division — a self-propelled (SP) AW battalion if attached to an armored division, and a mobile AW battalion if attached to an infantry division. A corps normally had one or more AAA groups attached. Each AAA group consisted of two or more automatic weapons battalions (usually mobile), although a gun battalion was occasionally attached. In the European Theater, gun battalions were more frequently found in AAA groups attached to the army or army group. Antiaircraft brigades were also formed and were normally attached to armies or to theater commands. In addition, the IX Air Defense Command (in effect an AAA division, originally organized as a part of the U.S. Ninth Tactical Air Force), with an average of 10 to 15 gun and automatic weapons battalions, formed a powerful AAA reserve for General Omar Bradley's 12th Army Group in Europe. Searchlight battalions, on the other hand, could be attached to either an Army or Air Force as part of an AAA brigade. The 225th, for most of 1944-45, was part of the 49th AAA Brigade and alternately attached to the U.S. 1st Army and the 9th Air Force, and wore shoulder patches for one or the other, or both. Rarely would an AAA man at the battalion level wear a patch of any brigade, division, or squadron to which his unit was attached.


Surplus 60-inch AAA searchlights
and generators after WW II.

How Did the AAA Searchlights Work? (Want More Details on this Subject? Go!)
SEARCHLIGHT BEAMS (41 K)   In the days just before World War II, large spotlights that looked just like those lights that Hollywood used at movie premieres were stationed near airfields and harbors. The men who manned the lights would listen for airplanes, then position the lights in the sky, focusing on the aircraft so they could be tracked and, if necessary, shot down (later, simply listening for planes would be replaced by new invention called radar).

1941 and 1942 were the golden years for searchlight manufacturers like the Sperry Gyroscope Company and General Electric Corporation. Ten thousand were made at a cost of $60,000 each, with most ending up in the U.S. Army where they served with antiaircraft searchlight battalions. These behemoths were conceived to light up the sky, searching for hostile planes. U. S. Army AAA searchlight battalions used them in conjunction with radar sets and machine guns to shoot down enemy aircraft in both the Pacific and European Theaters. The radar would pick up the target, relay instructions to a primitive computer attached to the light, which would track the target and, finding it, illuminate it. (Before radar was invented, the lights were directed by sound locators, which operated like giant ears that listened for approaching airplanes and automatically guided the lights based on where the noise came from; the sound locator basically amplified the sound of the airplane's engines.)

A WW I sound locator. This "technology" even saw service
into the early years of WW II. Radar made such cumbersome,
inaccurate methods of aircraft detection obsolete.

WW II searchlights being demonstrated.

The radar and the light were synchronized with AA machine guns, so the light moved where the radar told it to, and the guns followed the light. When the target was illuminated, the gunners would open fire. All of the connections between radar, light, and guns were made with cables laid on the ground. In addition, both the radar and light needed electrical power and separate generators were required, which meant more cable hookups. It took quite a while to set up a searchlight battery! Plus, there were special mechanics attached to the battalion to service all of this very complex equipment.

WW II 60-inch searchlights still in use
during the Korean War (click to enlarge).

   How do they work? The key component of a WW II–era light is its 180-pound, 60-inch-diameter highly polished mirror, which concentrates the intense light produced from a relatively tiny (one inch) electrical arc. The arc is the heart of the light. It's created from the mating dance of two carbon rods, each about a foot long (hence, carbon-arc searchlight). They resemble the leads from a giant pencil. One carbon rod is attached inside the light and another is fed through a hole in the center of the searchlight lens. (Supplying the electrical power for this miniature sun is a Hercules flat-head six-cylinder engine coupled to a DC generator.) The electrical arc is a highly luminous and intensely hot discharge of electricity between the two electrodes (represented by the end of the rods — one is positive, the other negative). The arc was discovered early in the 19th Century by the English scientist Sir Humphrey Davy, who so named it because of its shape. An arc is characterized by high current, low voltage, and indefinite duration. It is usually started when two electrodes carrying an electric current are drawn apart. At the instant the electrodes are parted, strong electric forces draw electrons from one electrode to the other, initiating the arc. The discharge consists of a current composed of these electrons and charged gas particles, called ions, that form between the electrodes. The first practical electric light, the arc lamp, made use of the arc formed between two carbon rods. The WW II searchlights worked the same way.

   During the war the lights were mounted on a four-wheel chassis and loaded into a trailer for towing. The generators also were four-wheeled and could be towed directly or aboard a trailer. During the Korean War, the WW II lights were put back into service along with their ultra-reliable power plants, often mounted on the backs of trucks as shown above and below.

A WW II light and generator mounted on a truck
during the Korean War (click to enlarge).

   Where are they today? Most were scrapped, but a recent guess by an industry insider puts the surviving number at about 2,500 worldwide. They shine on in the outdoor advertising business and in Hollywood, where the venerable 1940s units are still used at premieres and other events. They've been sighted on film as well, appearing in such movies as Die Hard, 1941, and Robocop.

A WW II light and generator mounted on a truck
operated by the Blue Ridge Skylighters (click to enlarge).

How Was Radar Used in WW II?
   First, a little technical description is in order. RADAR stands for RAdio Direction And Ranging. Radar locates an object by bombarding it with radio waves and measuring the time taken for the waves to go out and bounce back to the transmitter. As radio waves travel at a constant speed, a target's position can be fixed. How? An antenna sends out radio waves in short pulses. When a plane flies into the beam it reflects some of the waves back to the antenna. A transmitter/receiver hooked up to the antenna amplifies the signal and displays it on a cathode-ray tube as a blip of light on the screen marked off in miles. (A well-trained operator could also estimate the number of targets from the size of the blip and and could give their bearing and height.)


   In the First World War, there was no such thing as radar, or any form of electronic scanning device, so that the war was solely fought by eyes and ears. Whoever heard or saw the enemy first would have had more time to prepare. As far back as June 1932, there had been reports about a plane interfering with radio signals, and re-rediating (or reflecting) them. Thus Sir Robert A. Waston-Watt, A British electronics genius came up with an idea that he dubbed "RDF," or Radio Direction Finding, a discovery he formally submitted in a paper published in 1935. (According to an article in the July 1990 issue of Smithsonian magazine, radar had been "in the works" in Germany as early as 1933.) Not long after Watson-Watt's paper appeared, radar development surged ahead in England, France, Italy, Russia, and the United States. Only England, however, really pushed radar and its practical use. By the time the Nazis were ready to start the blitz of England in July 1940, England already had 29 radar stations forming an invisible curtain along its southern and eastern coasts. Operations command rooms had been established in several places in England to receive reports of the positions of ships and planes from the radars. There the decision was made on whether to use intercept fighters or antiaircraft fire, or both, to deter the targeted hostile bombers. This operations room coordination made the radar defense system effective ... but had not — unbelievably — been started in any other country! It's common knowledge that a few hours before the Pearl Harbor attack, a U.S. radar station on Oahu "spotted" the hundreds of Japanese planes approaching the island. But, without an operations command room to take action, their reports up the chain of command were useless and the rest, as they say, "is history."

   The Germans never developed and deployed radar to the extent the Allies did. At the end of the war, Nazi radar was not much improved over the sets they had captured from the British after the fall of France in June 1940. They had not seen the value of the tactical use of it other than on battleships.

Three soldiers sit in place at an SCR-268 gun-laying radar used by the 90th Coast Artillery in Casablanca, French Morocco.
Image courtesy U.S. National Archives and Records Administration.

   American AAA radar was first deployed in the North African and Italian campaigns, primarily for target tracking in conjunction with searchlights. These "gun-laying" sets were very primitive by today's standards. There was one cathode ray tube to show the distance a target was from the set, and a second to help pinpoint the direction. Both were inaccurate; it really took the plots from two or more sets to estimate where the target was, and guess the number of planes, and their altitude. However, operators soon learned how to get the most out of a single set, and a trained person could guide planes to that set (at an airfield), or vector a plane to intercept another.

   The radars were crude, set up in a tent. One man rode a sort of stationary bike to turn the set towards the target; a second turned a crank to point the antenna up or down while the operator watched the monitors!

According to an article in the September 1945 issue of Air Force, an official service journal:
The radar men who had to set up shop in many of our combat zones in the early days of the war had to be missionaries, salesmen, and electronics experts all at once. Not infrequently the highest ranking man in the group would be a second lieutenant, whose gold bars conveyed nothing ... about his long, specialized training in electronics labs on both the U.S. and England. He would arrive at some remote outpost with several tons of strange crates and some orders about setting up an aircraft warning system.

"It was sometimes a tougher problem to sell your own CO on the idea than it was to replace all your (equipment) ... sunk on the way over," said one veteran radar officer. "Most of the time you'd find that in the first place radar had been kept so secret that he hadn't the remotest understanding of what it was supposed to do. And then, being a 'fighting man himself' he'd distrust on sight a bunch of pampered (which we weren't but had to prove) lab technicians. You'd really be out of luck if his attitude also happened to be that of we-got-along-without-it-all-right-in-the-last-war-why-do-we-need-it-now? Anyway, who is a second looey to argue with an eagle?

"But after a few raids, particularly if our planes were caught on the ground, things would be different."

Even as late as the Anzio campaign the boys were having selling troubles. "A number of officers around there didn't have too much respect for the gadget until one night we happened to pick up a ground target and passed it along for routine investigation," related a member of a Mediterranean Signal Warning Company. "When it turned out to be six enemy tanks behind our own lines, tanks which nobody knew about until that moment ... well, our stock went up considerably."

SCR-584 unit (click to enlarge).


Typical deployment of an SCR-584.

   The 225th used two radar sets in their operations: the SCR-268 and the SCR-584 (SCR denoting Signal Corps Radio), but here's a little bit on each set used by the AAA forces throughout the war:
SCR-268 — Photos of one of the 225th's set are here and here .
SCR-271 — This was the first fixed radar system and resembled a very tall radio mast. Built for long-range detection, it was able to locate enemy aircraft up to 150 miles away. Constructed of steel with a special copper-coated steel dipole, the radar's antenna, which looked like a set of bedsprings from a king-sized bed, was mounted on a 100-foot-high platform and generally placed on a high mountain peak or ridge.
SCR-296 — More information on this coastal defense radar set is here.
SCR-582 — More information on this coastal defense radar set is here.
SCR-584 — The 584 was mounted in a van; the dish-shaped antenna was mounted on the roof and was set atop an elevator system that allowed the dish to be lowered when the set was to be moved. (No more getting a radar set off a truck, setting it up on the ground and draping a tent around it!) The presentation of information in the SCR-584 was on a big picture tube, which resembled a 25-inch TV screen, and data was much more accurate and easier to interpret thanon the 268, 270, and 271 units. The radars were UHF (ultrahigh frequency) sets of about 1 centimeter wavelength. The transmitters were powered by magnetrons, similar to the power unit in a microwave oven. The operations manual was a book the size and weight of a big city telephone directory!

Portions reprinted from The Military Memoirs of Gardener L. Friedlander.

What Were the Main Weapons of AAA Units?

   The weapons used by U.S. AAA units ran the gamut from giant flak cannon (left) to heavy machine guns (right). Click on a link below for detailed information about a particular weapon.    The photos below depict, top to bottom, a 3-inch AA gun; a T4 gun director for the 3-inch AA gun; and 75mm AAA guns firing at night.



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