One Century Ago: Breaking Ground for an Assembly Plant of Doom

This map from May 1917 shows many of the facilities that would be built at the St. Juliens Naval Ammunition Depot during World War I, including buildings for the largest mine assembly complex to be built up to that time.  (Courtesy of the Norfolk Naval Shipyard Archives)

Although the official opening of the new Naval Training Station at Sewells Point on October 12, 1917, made the front page (below the fold) of the Norfolk Ledger-Dispatch, it gave more prominent billing to a story about a new auto factory that was said to be in the works from Guardian Motors. A wire service story that ran in the middle of the page quoted the former head of Germany's Imperial Navy Office, Grand Admiral Alfred von Tirpitz, as saying, “We can continue confidently to expect a final triumph over England as long as we continue to sink vessels faster then she constructs them.” At the time, he was technically correct about the ongoing unrestricted submarine campaign that had very nearly brought the British to the negotiating table earlier that year. But on October 24, ground was broken on a special type of assembly plant, the largest of its kind in the world, that would render the German admiral's prognostications to be about as prescient as those of Guardian Motors.

The year before, the Royal Navy had deployed a series of nets and mines close to U-boat bases along the Belgian coast, but their Vickers Elia mine was so unreliable that German submarine officers sometimes used their harvested casings to create punch bowls for their messes. After the American entry into the war against Germany in April 1917, Rear Admiral William S. Sims, who had recently reported to London as the liaison to the British Admiralty, subscribed to their view that “To absolutely blockade the German and Belgian coast against the entrance and departure of submarines has been found quite infeasible.” adding in a message to Navy Secretary Josephus Daniels a couple of months later, “Nets do not stop submarines. Mine barriers can not be wholly effective.”

There were those within the Navy's Bureau of Ordnance (BuOrd), however, who did not agree with this assessment. Rear Admiral Ralph Earle, its chief, was convinced that mines, properly designed, constructed and deployed in sufficient numbers, were key to neutralizing the "hornet's nests;"a term President Woodrow Wilson was fond of using to describe the U-boat bases. Planning began at BuOrd for much larger and more sophisticated mine barrages, both in the North Sea and in the Adriatic, before the ink was dry on the declaration of war against Germany. Assistant Secretary of the Navy Franklin D. Roosevelt was a fan of the plan, but his boss, Josephus Daniels, was not, at least at first. He called the plan “A stupendous undertaking--perhaps not impossible but to my mind of doubtful practicability. North Sea too rough & will necessitate withdrawing all our ships from other work and then can we destroy the hornet’s nest or keep the hornets in?”

By September, President Woodrow Wilson had had enough with the British Admiralty’s handling of the war and agitated for a more proactive, assertive approach to be led by the U.S. Navy. Meanwhile, Sims, ostensibly in command of all the American naval forces being sent to Europe, was still maintaining the British line, telling Rear Adm. Earle, “It is by reason of the very bitter experience which the English and French have had in this particular respect that they are reluctant to accept a mine which is believed by those having no war experience to be superior to theirs. . . this is a good scheme if it works but a very expensive one if it does not.”

A diagram of the operation of the Mark VI mine. (Hampton Roads Naval Museum file)

By then, however, Earle was well underway with producing a mine far superior to that which had been produced by the British; which would make the idea of a barrage long enough to block an entire sea possible. Unlike the “horned” British and German mines with firing mechanisms that required close proximity to detonate, BuOrd pioneered the Mark VI mine and its “K-pistol” mechanism, which utilized copper wires extending above and below the mines to enhance its sensitivity. This would make it possible for fewer mines to deny a larger area to U-boat traffic.

As indispensable as he was as liaison to the British, Sims would not be the man to finally bring the Admiralty around to the more audacious American approach towards dealing with the submarine threat. President Wilson and Secretary Daniels dispatched Vice Admiral Henry T. Mayo of the Atlantic Fleet to London that month.  Daniels later remembered Wilson's exhortations to Mayo about the “absolute necessity of finding and ending the hornet’s nest, & destroying the poison or removing the cork. [Wilson] impressed upon them the need of an offensive and reiterated his view that we cannot win this war by merely hunting submarines when they have gotten into the great ocean.”

A diagram of the North Sea Mine Barrage shows the general location of the mines and antisubmarine nets crisscrossing the sea. The mines were spread in an area approximately 230 miles long from Norway to Scotland. The first operation in June 1918 laid 5,500 mines. The mines were laid in three areas titled “A” “B” and “C”. “A” was the center, and largest, section, “B” went towards the Orkney Islands, and “C” went towards Norway. Section “A” was purely American, but the Americans also provided mines to sections “B’ and “C”, which were mined by the British. Due to the efficiency and production of the Americans, the US Navy provided more mines to both “B” and “C” than the British. The width of the barrage went from 15 to 35 miles. The depth of the mines ranged from 45 to 260 feet.(Hampton Roads Naval Museum file)

At a “War Council” convened in London in September, Mayo made little headway with Russian, French, and Italian representatives, but crucially he was able to convince the First Sea Lord, Admiral John Jellicoe, to accept the plan. They ultimately settled upon a nearly 300-mile stretch across the North Sea, between the Orkney Islands north of Scotland and Norway. To him, its most attractive feature was that the barrage would be nowhere near German-controlled waters, where they had so effectively swept British mines the year before. But both men realized that if the plan was to work, an unbelievable number of reliable mines would have to be produced first. In any case, BuOrd had not waited around for the dithering British to make up their minds. The first contract for 10,000 Mark VI mines had been awarded on August 9, 1917, before Mayo even left for London. Even so, planners estimated that it would take a staggering 100,000 mines to block the North Sea.  On October 3, a contract for 90,000 more mines was approved.

Mine casings and other components on flatbed railroad cars await assembly at Norfolk Naval Shipyard in July 1917. (Courtesy of the Norfolk Naval Shipyard Archives)

Norfolk Naval Shipyard already possessed some mine construction capability, but there was no infrastructure in place there that could carry out such an ambitious plan. In any case, there was not enough room, so BuOrd turned to a Naval Ammunition Depot along St. Juliens Creek, about a mile south of the shipyard, which had existed there in one form or another since 1895. “A loading plant of this type and scale had hitherto been unknown not only in this country, but abroad,” wrote Earle of the undertaking. Some buildings could be upgraded, but almost two dozen new buildings would have to be built for mine assembly, the melting of trinitrotoluene (TNT), and filling of the mines, which contained 300 pounds of TNT apiece, plus cold-storage buildings to store the completed mines until they could be shipped. Railroad spur lines would also be required to deliver the mine components to assembly buildings. The shipyard continued to produce the casings for the mines, but BuOrd contracted other components out to different automobile manufacturers, making use of the private sector’s production capability for consumer goods, already the best in the world, for destructive ends.

Meanwhile, the British Admiralty dragged their feet. They did not officially allow the North Sea mining plan to go forward until November, weeks after construction began on the mine plant. Even with the necessary political will and financial support (on the American side, anyway), other obstacles remained. Not only were the ranks of able workmen drained by the ongoing Army draft, the workers who remained labored through one of the worst winters ever recorded in the Hampton Roads area, and construction nearly ground to a halt until February 1918.

This rare image shows the giant conveyor used to load minelaying ships and mine-carrying freighters at the St. Juliens Creek Ammunition Depot south of Norfolk Naval Shipyard. (Courtesy of the Norfolk Naval Shipyard Archives) 

Miraculously, the mine plant began producing the undersea death dealers in March. With a staff of 16 officers and 525 enlisted men, the assembly plant at St. Juliens turned out to be better than Rear Adm. Earle had even hoped, easily able to meet or even exceed their quota of 1,000 mines per day. During the remainder of the war, the facility assembled and shipped 73,000 mines, plus shipping an additional 17,000 that had been assembled at a smaller facility in Wisconsin. The conveyor system used to load the vessels on the Southern Branch of the Elizabeth River was the largest of its kind in the world.

By the time hostilities ended on November 11, 1918, 56,611 American mines, most of them assembled at St. Juliens, guarded the depths of the North Sea, with only 6,400 mines left to deploy before the American segment of the barrage was complete. All told, the North Sea Mine Barrage was credited with sinking six U-boats and damaging an equal number. It remains unclear how many submarine commanders avoided the open ocean because of the silent but deadly underwater wall, but anecdotal evidence seems to indicate that, at the very least, they finally developed a deep respect of the Allied mines. The following passage appeared in a history of the barrage that was published in 1919:

In connection with the enemy’s attitude toward anti-submarine measures taken by the Allies, it is interesting to note the statement of a captured German submarine commander who had had considerable experience on that particular type of vessel. He expressed the opinion that of all the anti-submarine measures which had been taken, mines were by far the most dreaded by the German submarine personnel, principally because there was nothing to indicate their presence. Also, because the quality of allied mines had recently been improved in a most unpleasant manner, the former practice of fishing them up and taking them home for conversion into punch bowls for submarine messes had now been entirely abandoned, he said.

Paraphrasing Sun Tzu, breaking an adversary’s will to fight without direct conflict and the perils that go with it is preferable to undertaking a direct assault. As expensive as it was, the construction of a mine barrage would have been less expensive than, for example, attempting a series of amphibious raids against U-boat bases. This massive yet invisible submarine barrier made possible what President Wilson had wanted all along: A way to neutralize the “hornet’s nests.” While Wilson had originally wanted the U-boat bases attacked directly, the more economical way to go, in terms of both blood and treasure, was deploying these mass-produced mines to form a great underwater wall, modifying the behavior of German commanders, eroding their will to fight, and ultimately neutralizing the threat they posed to the Allied war effort.