The Hammer of Hell
Chapter 1 — The Coast Artillery Joins the Army:
The Creation of Antiaircraft Artillery

In April, 1941, General George C. Marshall, the Chief of Staff of the United States Army, sent a memo to the Operations Division of the Army Staff directing them to study the creation of "mobile antitank and antiaircraft units organized at the corps and army echelons" to counter the German blitzkrieg.
1 Marshall wanted a combined arms force which was capable of rapid movement and aggressive offensive tactics.

For an American Army that was still attempting to escape from the doctrinal lessons of World War I, it was a tall order. The Antiaircraft Artillery role had to be significant, for in Poland and France, the Luftwaffe made a fundamental contribution to the blitzkrieg's successes. The defense of the field army, and especially the most forward of all combat troops, the maneuver divisions, had been under discussion for two decades. Its genesis was in the interwar Coast Artillery Corps, which had successfully defended the United States against sea attack since 1907. The Coast Artillery's stepchild, the Antiaircraft Artillery, gave the branch a tactical mission and the Coast Artillery spent the 1920's and 1930's in a resource-constrained environment searching for a solution. But prejudices and unproved expectations relegated the antiaircraft to employment in the corps rear until the late 1930's, when the War Department recognized the requirement to improve the AAA protection for its divisions and corps. The Antiaircraft Artillery doctrine, tactics, technology, and structure introduced between 1939 and the Battle of Kasserine Pass reflected the Coast Artillery mentality and the indifference of the U.S. Army towards air attack in the combat zone.

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A Coast Artillery crew fires a 12-inch mortar at Fort MacArthur, California, 1920s.  (Courtesy of Fort MacArthur Museum.)

Interwar Attitudes Toward Antiaircraft Artillery
The officer who built the American Army that fought in World War II was Lieutenant General Leslie J. McNair, the commander of the Army Ground Forces. Following Marshall's guidance, McNair believed that the doctrinal objective for the AAA was: "Antiaircraft fire to protect ground needed in a mobile mass sufficient to meet concentrated aerial attacks."
2  Like the other specialized branches of the Army, the tank destroyers and armored forces, McNair believed that the Antiaircraft Artillery protection of combat forces was an infrequent necessity. McNair decided that these forces should not be organic to the division; instead, they should be held at corps and allocated forward when needed.

The Luftwaffe operations in Poland and France seemed to dictate that antiaircraft units would be needed along the forward line. In those campaigns the German Air Force, or Luftwaffe, opened with surprise attacks against the opposing air force, which often caught them on the ground, and then conducted close air support and interdiction operations. German dive bombers and fighters initially provided the fire support that helped to rupture the enemy line. Once this action was completed they turned their attention to eliminating those pockets of resistance that impeded the advance of the tanks. Because the German Army controlled the air, the Luftwaffe was at the most critical spots on the battlefield. The Luftwaffe seemed to be everywhere, simultaneously strafing front line units and harassing refugee columns well to the rear.3

The lessons learned from the actions in France and Poland indicated American Antiaircraft Artillery must be responsive at all echelons and that all levels must have the ability to give concentrated coverage when needed. The fundamental building block of the American Army was the division, yet McNair opposed making an Antiaircraft Artillery unit part of (organic to) the division throughout the war, though the issue continued to surface. He simply did not think that there was a continuity of need.

At the Army War College from 1929 to 1931, students debated the air defense of the division. The students believed that the best protection within the infantry division against low-altitude attack was the training of the individual soldier to aggressively use his assigned weapon to engage enemy airplanes. In 1933, the Infantry School stated that front line units could provide a "large degree" of the necessary antiaircraft protection by themselves. The Antiaircraft Artillery was assigned to corps, and it afforded protection for corps assets against high-altitude bomber attacks. According to the students, bombers posed no threat to the widely dispersed front line infantry units. Consequently, the Coast Artillery and its weapons were not needed.4 Army leaders and junior officers in the combat arms were convinced the air threat to the division could be defeated, largely by avoiding detection from the air. This thinking reflected American doctrine which stressed night operations, the use of camouflage and organic small arms for defense versus air attack.

From 1925 until 1932, three consecutive Chiefs of Coast Artillery recommended that the Antiaircraft Artillery should be part of the division. They argued that enemy fighters could attack below the antiaircraft gun coverage provided in the corps rear area, and infantry units were thus susceptible. While they admitted that the infantry did have a significant self-protection capability, the coast artillerymen believed engaging enemy aircraft was a secondary mission for them, and dedicated gunners were necessary. Furthermore, divisional operations were more fluid and in closer proximity to the enemy, which created a new set of training and operational problems that could only be resolved through repetitive training.5

These recommendations fell on deaf ears. Until 1935 the American Army saw divisional operations as set piece affairs; the opposing armies would march toward each other, organize themselves in assembly areas, and then move to the front. The Coast Artillery thought divisional Antiaircraft Artillery units were needed to protect the routes to the front, an estimated distance of 10 to 20 miles, and the divisional assembly areas, which covered an area of several square kilometers. Since the antiaircraft guns of the time could not engage targets below 5,000 feet, the defense against the low-altitude fighter fell upon the single-barreled .30- and .50-caliber antiaircraft machine guns, first developed during World War I. Optimistically, these AAA machine guns had an effective range of 1,500 yards, so it required almost 100 systems to cover a 20-mile route of march. To an American Army intent on keeping the size of the division as small as possible, adding that much force structure to the division was not acceptable. The infantry could defend itself pretty well anyway.6

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The 50-caliber, water-cooled machine gun was first developed during World War I. It had an effective range of 1,500 yards.

In 1932 the War Department decided that Antiaircraft Artillery would not be organic to the division.7 Organic AAA would remain a dormant issue until 1942 when General Jacob Devers, the commander of the Armor Command, wrote McNair asking for organic Antiaircraft Artillery for his tanks, based on the mobile, independent nature of armored operations.8 McNair replied to his request and a similar one made by General Dwight D. Eisenhower shortly after the North African invasion with the same argument: Antiaircraft Artillery was not needed all the time; the infantry could defend themselves; and, if necessary, pooled antiaircraft units at corps could be assigned missions in divisional areas.9 McNair's continued resolve was the product of his judgment and the prejudices that he and most other Army combat arms officers held about coast artillerymen.

In the 1920s and 1930s the American Army derogatorily called the Coast Artillery the "Red Comforter Corps." While most Army officers practiced their profession at Fort Benning, Georgia, Fort Bliss, Texas, or Fort Warren, Wyoming, coast artillerymen manned beautiful old fortifications. Rubbing salt in the wound, the Coast Artillery posts had to be located in major seaports: New York City, Norfolk, Los Angeles, San Francisco and overseas in Hawaii, the Philippines and Panama. On Saturday nights, infantry officers had a drink on the porch of their quarters while coast artillerymen went to Times Square.10

After 1932, coast artillerymen became physically and mentally separated from the rest of the Army, even though senior Coast Artillery Corps  officers attended the Command and General Staff College and the Army War College. In the 1930's , the American Army began to seriously discuss the integration of the tank and the airplane into existing doctrine, but the U.S. Arm remained an infantry-centered Army, even though sufficient changes had occurred to warrant serious study. Coast artillerymen were not oblivious to these developments, but their focus remained on the seacoast defense mission. In 1941, General Marshall appointed Coast Artillery generals to command three activating corps. He removed them several months later because they did not understand "mobile warfare" and because they lacked initiative.11

Coast artillerymen were not accustomed to the pace of an activating unit. They lived and worked in an environment where the mere presence of their coastal installations provided sufficient deterrence, and where the threat and the guns to counter it had not changed for 30 years. Captains commanded the seacoast batteries and their routine was so established that Coast Artillery field grade officers were comfortable occupying themselves with administrative, rather than operational matters.

While the development of new Antiaircraft Artillery equipment was a challenging mission, coast artillerymen remained seacoast artillerymen first and antiaircraft artillerymen second. It was not until the early 1930's that the branch made an effort to insure that all coast artillerymen had some antiaircraft experience. Even in the late 1930s, the chiefs of Coast Artillery were still telling young Coast Artillery Corps officers that they would not be allowed to specialize in Antiaircraft Artillery, even though many of them believed that AAA was the future of the branch.12

This preoccupation with the seacoast mission, the rejection of their attempts to become part of the division, and the perception by senior Army leaders that there was no continuous need for Antiaircraft Artillery to protect the front line of troops dictated the American Army's forward area antiaircraft doctrine. Consequently, both structure and technology would be dilatory in responding to the requirements of the blitzkrieg. Compounding the problem, the underpinning Antiaircraft Artillery doctrine for the defense of the field army was controversial and widely misunderstood.

Interwar Antiaircraft Artillery Doctrine
During World War I, the American Army countered German low-altitude attacks against the Allied front lines and higher-altitude bombings of major industrial and urban centers with a composite force of borrowed French 75mm guns, machine guns that were modified for the antiaircraft role, and search lights. This embryonic antiaircraft force defended key points along the trench lines and critical facilities in the rear areas.

In 1923, the Coast Artillery organized the Antiaircraft Artillery battalions into two-battalion regiments to provide a complete capability against both low- and high-altitude air attack. The first battalion had the somewhat immobile 3-inch AAA gun, developed in America during World War I, but never shipped overseas. The antiaircraft gun battalion had four batteries with three guns each and a battery of searchlights. The second battalion was termed the automatic weapons battalion, although it was equipped with the single barreled .30- or .50-caliber machine gun mounted on the AAA pedestal.14

Coast Artillery Corps soldiers fire a 3-inch gun at Fort Ontario. The gun could fire a projectile more than 15,000 yards, but its crude fire control reduced its effective range to less than 5,000 yards.

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In 1925, the Coast Artillery conducted a study for the Adjutant General to determine the Antiaircraft Artillery requirements for the defense of the field army. The study concluded that the antiaircraft defended two categories of targets: key transportation and logistical facilities in the rear areas and forward combat units. Since the threat to the corps and army rear areas was the bomber, guns were allocated to the defense. Specifically, in a typical corps area, four 3-inch AAA gun batteries (one regiment) could defend all the vital facilities in the corps rear, and their overlapping coverage created an area defense over the entire corps rear area and parts of the divisional rear areas. The automatic weapons battalion provided low-altitude defense for the most critical spots in the corps rear area.15

An area defense was at the opposite end of the doctrinal spectrum from the WWI antiaircraft experience. In WWI, antiaircraft artillerymen admitted that their systems were inaccurate and short ranged, so they were compelled to position the guns and machine guns close to the defended target where attacking aircraft could be engaged in an incoming posture, the easiest AAA gunnery problem. This conservative tactic enhanced individual system accuracy and enabled multiple guns or machine guns to engage the same airplane. The objective was to produce a volume of fire that would drive the enemy aircraft away; killing the aircraft was a secondary consideration. Marginal capabilities dictated a doctrine of point defense.

In 1925 the suggestion of an area defense meant that the Coast Artillery regiment had the ability to accurately fire anywhere within the effective range of their guns, regardless of the enemy tactics. The report specified that area coverage was possible against a bomber flying about 100 miles-per-hours on a flat and level approach. Unfortunately, the gun coverage diagram was extended to all aircraft without regard for altitude or speed. On this basis Army officers and politicians came to believe that a Coast Artillery antiaircraft regiment could create a protective umbrella over an Army corps, from the ground up.

In retrospect, the 3-inch AAA gun could fire a projectile over 15,000 yards, but its effective range was reduced to less than 5,000 yards due to the crude state of the weapon's fire control. An area defense required accuracy, and the improvement of fire control (a technical and complicated problem) became an obsession with the Coast Artillery.16

In 1930 the Coast Artillery adopted the first American-designed director, the Sperry M2. This director, like its predecessors, computed data mechanically. It predicted where the round would intercept the aircraft, and this information was telephoned to the gun crew. In later models, once altitude and direction to the target were determined the director chief dialed in the speed of the target. The director predicted where the round would intercept the aircraft in space and sent the required adjustments to the gun. The Coast Artillery spent the interwar years attempting to automate the computation of the intercept point, the transmission of the altitude and azimuth settings to the guns, and in reducing the time necessary to load and set the fuse on the 3-inch round, which caused it to self-distruct at a given range. Range, rate of fire, and accuracy were the primary design considerations for AAA guns. Mobility---the ability to rapidly emplace and displace the systems---was a consideration, but a secondary one.17

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Directors computed firing data mechanically and predicted where rounds would intercept target aircraft. In later models, crews tracked targets though sights aligned with those on the 3-inch guns.

The speed of the airplane doubled between 1920 and 1939, but the Coast Artillery was unable to develop fire control devices that kept pace. These technical difficulties made the 3-inch AAA gun obsolescent by 1933. Even in 1925, before the quantum improvements in aircraft technology began, the Coast Artillery had a number of critics, including officers in the branch such as General Johnson Hagood. Hagood attended an Antiaircraft Artillery demonstration at Fort Monroe with his good friend, General William Mitchell, about the time of the study. Thousands of 3-inch gun and AAA machine gun rounds were fired against a sleeve pulled by an airplane. When the target was retrieved, there had not been a single hit!18 The Coast Artillery was suggesting an area defense using the same equipment. The study had lasting significance because from the 1920s through world War II   Army mobilization plans allocated a single Coast Artillery regiment per corps.

In 1933, the Coast Artillery School updated the 1925 study and concluded that two AAA regiments were necessary to defend "the most vital point targets in the corps rear area" against a 180-mile-per-hour threat. Any suggestion of a high-altitude gun overwatch of the combat zone was gone. Because of the economic depression, in 1932 the War Department disapproved the Coast Artillery proposal. After some negotiation the Coast Artillery suggested adding just one battery---four 3-inch AAA guns---to each gun battalion. This modest increase was also tabled for monetary reasons.19 Due to the inability to add structure to compensate for the lack of a modern capability, an area defense doctrine was a doctrine of impotence.

Five years later, three antiaircraft regiments participated in an air defense exercise at Fort Bragg, North Carolina. Antiaircraft artillerymen teamed with Air Corps pursuit aviation squadrons to defend the post against simulated bomber attacks. After the exercise, the participants agreed that the 3-inch gun lacked the range to engage the bombers, which flew above 20,000 feet. The results were described as disappointing in the Coast Artillery Journal.20

Despite the continuing setbacks, the doctrinal objective for the Antiaircraft Artillery was not updated. Even after a decade of technological disappointment during which antiaircraft fire control failed to keep pace with the ability of the airplane to fly faster and faster, the Coast Artillery took no action to redefine their role in support of the field army. The impression remained that an Antiaircraft Artillery regiment per corps was sufficient. In 1938, General John J. Pershing wrote that despite the German successes in the Spanish Civil War the Antiaircraft Artillery was still dominant over the airplane.21

About the same time, Senator Morris Sheppard of Texas described American Antiaircraft Artillery equipment as the best in the world.22 Major General A. H. Sunderland, the Chief of Coast Artillery from 1936 until May 1940, thought that American Antiaircraft Artillery equipment was current. His major concern was that the United States needed much more antiaircraft equipment.23

In 1937, the appropriations for the Coast Artillery increased 12 times over the yearly average for the previous 17 years. General Sunderland believed that the AAA gun remained the cornerstone of the antiaircraft force and he devoted most of the budgetary increases toward the development and standardization of a new big gun, the 90mm, which had more range and a radar to improve its target acquisition. The 90mm gun, M1, was approved for production on 21 March 1940. The M1 was a great improvement over the 3-inch AAA gun, as it fired to an altitude of 39,000 feet. The gun was designed for use an an antiaircraft weapon. Its carriage had two road wheels that had to be folded back, and outriggers emplaced, before firing. The gun could not be depressed below zero degrees elevation, and because of the awkward carriage, without crew initiative, it was not an outstanding antitank weapon. The 90mm gun, M2, was standardized in May 1943. It had four road wheels and could be fired from the travel configuration. Fielded in 1940, the 90mm gun's capabilities would not be tested until the Battle of Kasserine Pass.24 Pessimistic coast artillerymen expected the 90mm to provide an improved defense for point targets in the corps rear; optimists hoped for an overwatch for at least a portion of the corps area.

While internal analysis and external expectations caused the Coast Artillery to focus their doctrinal thinking on the defense of the corps rear area, they remained candid about their inability to defend the units in contact with the enemy. The strong emphasis on gun development occurred after 1932, after the War Department rejected the Coast Artillery's attempts to include Antiaircraft Artillery in the division. The Coast Artillery, the most technically oriented branch in the United States Army, concentrated on the development of big guns and fire control because it was their inclination to do so and because it was the only antiaircraft mission assigned to them.

In 1939, the low-altitude Antiaircraft Artillery capability in the United States Army was resident in the automatic weapons battalions in the Antiaircraft Artillery regiments. The AAA machine guns provided low-altitude coverage for the assets protected by the regiment and complemented the gun battalion. Independent operations by the automatic weapons battalion were considered unfeasible.

That year, the War Department directed the Coast Artillery to create separate Antiaircraft Artillery battalions that could operate without regimental logistical assistance and provide low-altitude antiaircraft defense. The Coast Artillery objected, arguing that the regiment was the only organization capable of defense against fighters and bombers, both day and night. The Army staff understood, but argued that the management of Coast Artillery regiments during mobilization was onerous due to the broad variety of weapons and personnel specialties found in the organization. Finding one location for a regiment to train was difficult.25

Concerned that the regimental organization was at risk, the Coast Artillery did another study that concluded, a year after the Fort Bragg exercise, that one AAA regiment could provide sufficient protection for the "establishments" in a maneuver corps. Sensitive to the War Department's apparent concern about the low-altitude protection of forward area facilities evidenced by the separate battalion initiative, the study suggested the regimental automatic weapons battalion could be used in the divisional rear area to counter the enemy's main effort by protecting point targets in the vicinity of the enemy's main attack. 26

General Malin Craig, the Chief of Staff of the Army, approved the results of the study and directed that one two-battalion AAA regiment would be allocated to each corps. He also directed the creation of the separate battalions.27

With the mission now assigned to provide an independent low-altitude capability, the Coast Artillery scrambled to provide the separate battalions with a low-altitude gun, which could also be issued to the regimental AW units, to fill the gap between the 3-inch gun's minimum altitude and maximum elevation of the AAA machine guns.

In early 1940, the leading candidate was the Browning 37mm gun, which Army officers had first seen in 1924. Initially, its carriage was unstable when fired, but that was corrected by the end of the decade. The gun remained prone to jamming, but it did have a range of around 1,000 yards. It had no fire control, and it did not have a high-explosive round, considered essential to knock down an aircraft. Desperate, in the fall of 1939, the Coast Artillery standardized the 37mm gun and initiated its production.28

Because the Coast Artillery Corps was not satisfied with the 37mm, in September 1940 General Marshall asked the British for the loan of four Bofors 40mm guns with their Kerrison Predictors for testing. The subsequent firings were most impressive. The Kerrison Predictor provided accurate fire control to a range in excess of 1,500 meters, and the Bofors gun was reliable. In the fall of 1940, the Ordnance Department standardized the Kerrison Predictor for use with the 37mm gun. By February 1941, the United States Navy adopted the Bofors for use on their ships. To ease production problems (the United States was building the Bofors for the British under the Lend Lease Program), the Army reluctantly standardized the 40mm in February 1941.29 Like the 90mm gun, the 40mm gun had a director, which suggested the promise of more coverage.

The Coast Artillery School would not publish doctrine for the separate battalions until 1943. During 1941 and 1942 the students at the Antiaircraft School at Camp Davis, North Carolina, were told that 40mms should be used to protect point targets in the division. If those priorities were carefully selected a low-altitude blanket might be created just behind the forward line of troops---a pseudo area defense.30

The command arrangement was clear, the separate battalions would be attached to the divisions. In 1937, as part of the Army's test of the triangular division organization (which was used during WW II), an Antiaircraft Artillery battalion, which had AAA machine guns mounted on trucks, supported the test organization and protected the division's assembly areas, marshalling yards, and tactical convoys. The antiaircraft artillerymen were attached to the division, which placed them under the division commander's operational control, but they were not a permanent part of his organization. The conflicting requirements of control and of keeping the division small had thus been resolved.31

The director could not solve a fire control problem for aircraft within 600 meters of the gun because of the extreme closing speed of the target, so the separate battalions were organized with 32 Bofors and 32 AAA machine guns. One machine gun protected the dead zone of each Bofors gun.

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Thousands of 90mm, left, and 40mm antiaircraft guns, right, began pouring off American assembly lines as the Untied States geared up for war.

By 1941, the Coast Artillery was in the midst of a metamorphosis toward implementing an antiaircraft defense of the field army. Although the branch realized that their defense of a corps area was limited to "establishments" in the corps rear, the common perception was that the Antiaircraft Artillery would do more, especially when equipped with the new 90mm gun. In 1939 the War Department assigned the defense of the division to the Coast Artillery. Within two years the Antiaircraft Artillery Command created the necessary organizations, equipment, and command relationships for the separate AW battalions when employed in the combat zone. Without the benefit of training maneuvers, and encumbered by the belief that AAA was not continually required, when war came, providing the antiaircraft defense of a maneuver division was like opening the door to a darkened room with a new flashlight---no one knew how far they could see or what was in the room. Doctrine would emerge in the light of combat.

Chapter Two
The Hammer is Formed: The Antiaircraft Command