World War II Harbor Defenses

For more than a century before World War II harbor defenses had constituted the primary element of the means employed by the Army for seacoast defense. Harbor defenses consisted of permanently installed guns of various calibers, which could be supplemented in an emergency by mobile coast artillery guns and controlled mine fields. Their purpose was, first of all, to guard the defended area against invasion and capture; secondly, to protect the area against naval bombardment, and shipping against submarine or surface torpedo attack; and finally, to cover the seaward approaches to the principal naval anchorages sufficiently far out to enable ships of the United States Navy to emerge and meet attack. Indeed, the location of naval shore installations and fleet anchorages was the most important factor in determining the location of Army harbor defenses, and the Navy's insistence on the necessity of such defenses was the principal reason for their retention and improvement during World War II. Adequate protection of bases and ships in port freed the Navy for offensive action. The War Department was also well aware of the fact that the maintenance of permanent seacoast defenses gave major coastal cities a sense of security which might help to ensure against an unsound dispersion of the Army's own mobile ground and air forces in a war emergency.

For a good many years before World War II the Army had recognized the inadequacy of existing harbor defenses. They offered no protection against aerial bombardment, and, since most seacoast guns were outranged by modern naval armament, they could no longer guarantee defense against naval bombardment. In studying the situation in 1923, the War Department decided that either a larger fleet or a much larger number of aircraft would provide more effective protection for harbor areas than the existing defenses, but it also held that the use of either would be highly uneconomical. It concluded, "when it comes to preventing enemy ships from sailing into a harbor and taking possession, the cheapest and most reliable defense appears to be guns and submarine mines."

Primarily for the latter reason, the General Staff decided in 1923 that permanent seacoast fortifications should still be considered essential. It recommended the abandonment of a number of harbor defenses that were no longer of military value and concentration on the improvement of those remaining, particularly by providing them with new long-range guns and more antiaircraft protection. It also urged more combat aviation to supplement harbor defenses. It called for the retention of permanent defenses for eighteen coastal areas-the same eighteen that were to be included in the modernization program of 1940 and that still possessed fixed defenses in 1945.

Between 1923 and the onset of the war emergency in the early summer of 1940, the Army gave a good deal of thought to the improvement of harbor defenses. It drafted new defense projects for each harbor area between 1930 and 1932, and in 1931 it established a Harbor Defense Board to supervise the execution of these projects and outlined the basic policies that were to guide the board in its recommendations. As a result of the growing tension between the United States and Japan, most of the meager funds available for harbor protection between 1933 and 1938 were spent on improvements along the Pacific coast. The threat of war in Europe in 1939 prompted larger appropriations and the resumption of work on gun installations along the Atlantic front.

The end of naval armament limitations during the 1930's had also reemphasized the need for better long-range guns; to meet this need the Army had adopted the 16-inch barbette carriage gun as the standard harbor defense weapon against capital ships, but only a few had been installed. Existing harbor defense projects called for many other improvements, and it was estimated in February 1940 that to complete approved projects would cost about $60,000,000. Three months later, the Chief of Coast Artillery described the existing defenses in these terms: "With but few exceptions our seacoast batteries are outmoded and today are woefully inadequate. Nearly every battery is outranged by guns aboard ship that are of the same caliber. More alarming than this is the fact that every battery on the Atlantic Coast, and all but two of the batteries on the Pacific Coast, have no overhead cover so are open to attack from the air."

Despite his protests, the War Department decided that the general shortage of antiaircraft guns was so critical that no mobile and no more fixed antiaircraft guns could be included in harbor defense projects.

The Harbor Defense Board was engaged in a resurvey of seacoast defense needs at the time of France's downfall in June 1940. Until then, the possibility of any naval attack on the American coast line had appeared very remote; thereafter, at least until the fate of the British and French fleets became known, the United States faced the real possibility of serious naval inferiority in either the Atlantic or the Pacific. The new naval outlook resulted in an enlargement of the current survey into a complete reassessment of harbor defenses.

The board's report of 27 July 1940 recommended the general adoption of the 16-inch gun as the primary weapon and the 6-inch gun as the secondary weapon in all fixed harbor defenses. It proposed that defense projects include 27 new 16-inch two-gun casemated batteries and partial air cover for 23 primary batteries (including ten 16­inch) already installed or previously approved. The 16-inch guns had a maximum range of about twenty-five miles, and, at least theoretically, could keep any hostile ship at a safe distance from any of the twelve harbor areas where they were to be installed. The board also proposed the construction of 50 new 6-inch two-gun barbette carriage batteries, which would provide long-range fire (about fifteen miles maximum) against cruisers and other lighter ships, and which would greatly reinforce the 63 existing secondary batteries (mostly 6-inch and 3-inch semimodern barbette carriage guns) that were to be retained. Its plan called for the abandonment of 128 obsolete and obsolescent seacoast batteries as soon as the 77 new batteries were installed. Thereafter, too, coastal defenses could be manned with substantially fewer troops. The board estimated that the whole program would require three years to complete and would cost about $82,000,000-less than the cost of one new battleship.

After careful consideration the General Staff approved the proposed modernization program. Informal questioning of the senior members of the Navy's War Plans Division elicited the unanimous opinion that, in the absence of the fleet, land­based aviation alone could not be considered a sufficient defense against naval attack. In the Army only the Chief of the Air Corps disagreed with this opinion. He thought that airplanes could be safely substituted for land-based guns in coastal defense. The formal approval given the modernization program in early September 1940 was accompanied by a recommendation that $62,000,000, or about three-fourths of the estimated total cost, be allotted for construction and contract authorization through 30 June 1942.

The planning, construction, and emplacement of seacoast guns and their auxiliary equipment took a long time under the best of circumstances. This was particularly true of the big guns. From the beginning the 1940 modernization program had to compete with the general and rapid expansion of the whole Army, and the program was also slowed by the continuously expanding naval construction program. By July 1941 only four 16-inch gun batteries were ready for action, and construction work had been started on only five others. By then it appeared that the 16-inch gun program could not possibly be completed for several years and that in the meantime the planned expansion of American air and sea power would make the full program unnecessary. After rearguing the merits of airplanes versus guns in seacoast defense, the War Department in the late summer of 1941 decided to limit active work to those batteries that could be completed by 30 June 1944. As a result all work on fourteen of the thirty-seven 16-inch batteries planned for the continental United States was indefinitely deferred. 11 The expansion of overseas base activity during 1941 was an important factor in delaying the continental 6-inch gun program, the War Department in November giving priority to the completion of twenty 6-inch gun batteries in outlying bases. 12 In consequence, the condition of the continental fixed harbor defenses on the eve of Pearl Harbor was not much different from what it had been before the adoption of the modernization program fifteen months earlier.

The Army's mobile coast artillery in the continental United States in December 1941 consisted of six tractor-drawn 155-mm. gun regiments and parts of one 8-inch gun railway regiment. At this same time there were thirty-one regiments and three separate battalions of fixed-gun harbor defense units in the United States or, roughly, five times as many fixed-gun forces as there were mobile.13 Plans in the 1930's had contemplated using a much larger proportion of mobile guns, particularly of railway guns, to supplement fixed-gun defenses in wartime. But railway artillery had such limited tactical mobility and such extreme vulnerability to air attack that it had been all but discarded as a coastal defense weapon before the United States entered the war. 14 After Pearl Harbor, railway guns were used at a few east and west coast locations but were replaced as soon as other weapons became available. Pending the completion of approved 6-inch gun projects, the Army used 155-mm. gun batteries to cover their positions; and sixteen batteries of these guns had been installed along the Atlantic front by December 1941. During the war the Army made much wider use of tractor-drawn batteries, placing them at many points along the Atlantic, Gulf, and Pacific coasts. It used at the maximum seventy-two 2-gun batteries, both to bolster permanent harbor defenses and to provide temporary protection to ports that had no fixed-gun installations. For a while during 1942 the Army also drafted field artillery batteries of 75-mm. guns and 105-mm. howitzers into coastal defense service. This proceeding was reversed at the beginning of 1944 when the Army discontinued the use of mobile guns in coast defense at home and put coast artillery weapons of this type into field service.

In each harbor the device for managing all of the defenses was the harbor entrance control post, manned by both Army and Navy officers. A joint directive defined the mission of these posts as follows: "To collect and disseminate information of activities in the defensive sea area; to control unescorted commercial shipping in the defensive coastal area; and to take prompt and decisive action to operate the elements of the harbor defense, in order to deny enemy action within the defensive coastal area."

Harbor entrance control posts began to appear during 1941. Throughout the war they were maintained at all defended harbors, providing the main link between higher command headquarters and all subordinate elements of a harbor defense. It was generally believed during the war that these posts permitted a close interservice co-operation that gave the whole harbor defense system a high degree of potential efficiency, but the enemy's failure really to challenge the system leaves this a matter for conjecture.

Until 1940 fixed harbor defenses were maintained on a caretaking basis, and the guns were not actually manned except at a few forts for training purposes. Regular Army harbor defense forces numbered about 4,200 men in 1939-less than one-third of the number regularly maintained in harbor defenses before World War I and less than one-tenth of the number that would have been required to man the existing equipment with only one relief. Army mobilization plans in 1938 and 1939 contemplated that the National Guard would provide the bulk of the approximately 50,000 troops that would be needed for harbor defenses in wartime, but National Guard units of this sort numbered only 7,000 men in 1939. 22 There was little change in harbor defense strengths until the fall of 1940, when the induction of the National Guard into federal service permitted the partial manning of all active installations. As the rehabilitation and reinforcement of harbor defense posts continued through 1941, units were recruited to full strength and all fixed guns were manned and put in operating condition. By the fall of 1941 the strength of harbor defense forces was approximately 45,000, and they were almost the only troops specifically assigned by the Army to continental defense until the formal entry into war in December.

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