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History and Heritage

Remembering the Great War

5 Key Naval Innovations

One hundred years ago, convoys of troop ships, protected by U.S. Navy escorts, began to regularly arrive "over there" in France, transporting waves of American ground troops to join the Allies and fight the Kaiser in the churning bloodbath that was trench warfare. And while the Great War may not be remembered as a great naval war, it did lead to a number of advancements and innovations that would change warfare and the Navy forever.


The signature naval weapon of World War I was the submarine. Various inventors had experimented with diving boats and underwater boats since at least the 17th century, and they made appearances in both the Revolution and the Civil War. The U.S. Navy then commissioned its first true submarine, USS Holland (SS 1), in 1900. German officials also saw potential in the new technology. They needed a way to counter the naval might of the United Kingdom, said Dennis M. Conrad, a historian with the Navy History and Heritage Command, and seized on the submarine.

In fact, Germany went from one undersea boat in August 1905 to 28 in the first two months of the Great War to 61 by June 1917, according to Fraser M. McKee in "An Explosive Story: The Rise and Fall of the Common Depth Charge." The U-boats proved remarkably successful, sinking nine British warships in only two months early in the war. The Germans also used their submarines to terrorize the Allies and blockade the United Kingdom, attempting to starve the British out of the war. They haunted Allied shipping lanes across the Atlantic, sinking millions of tons of freight and killing thousands. When the U-20 torpedoed the Lusitania in May 1915, for example, some 1,200 people died, including 128 Americans. Germany's avowal of unrestricted submarine warfare, Jan. 31, 1917, finally brought the U.S. into the war.

America ramped up its own submarine production in response. "They were the first submarines Americans built that could actually go to sea with any confidence that they would actually come back," said Conrad, although they still couldn't dive very deep or stay below the surface for very long. "The submarines were primitive and living conditions were very difficult. They were driven mostly by batteries. ... These batteries tended to leak acid. If you got them wet at all, they could discharge a poisonous gas."

World War I submarines also had limited success with torpedoes. They just didn't have room to carry many. Instead, they usually surfaced and used topside guns to sink merchantmen. They underwent major improvements in the 1920s and 1930s, "so by World War II, they are a significant factor," said Conrad.

Three photo collage WWI-era submarines.

Depth Charges and Mines

Naval planners needed a way to counter this new, dangerous weapon. After a number of creative attempts, including hand charges, towing charges and a variety of nets that extended from ships, researchers landed on depth charges. According to McKee, the British Royal Navy first developed the technology in 1914. After America joined the war in April 1917, it adopted and improved the British version.

"Initially, the delivery systems were primitive - merely rolling off the stern of the destroyer," said Conrad. "The number of 'ash cans' carried was small, the charges unreliable and the explosive power inadequate, but as the war progressed, the depth charges and the tactics used to deploy them became more sophisticated, and their use increased exponentially."

By the end of the war, U.S. depth charges carried 300 pounds of explosives and could detonate up to 300 feet below the surface, according to the Destroyer Escort Historical Museum. Depth charges were responsible for sinking more than 20 U-boats. Like submarines, they evolved a bit during the 1920s and 1930s, and came into their own during World War II.

However, as Conrad pointed out, depth charges weren't the only underwater explosives in the Navy's arsenal. They weren't even the preferred explosives.

"Throughout the war," he explained, "the U.S. Navy believed that mines, rather than depth charges, would defeat the submarine. In particular, the Americans created the North Sea mine barrage stretching from Scotland to Norway to prevent German submarines from entering the ocean from their home waters. The barrage was barely operational when the war ended, so it is impossible to know if it would have been effective."

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In addition to dropping depth charges, destroyers played another key role in confronting the underwater ghosts that "wreaked havoc" on shipping lanes in the first quarter of 1917. To get men and cargo through the submarine-infested Atlantic, Allies turned to convoying, using destroyers as escorts, according to Conrad. Historians debate whose idea it was, but Conrad believes the British came up with the system, and after a couple of convoys made it across the Atlantic without losing any merchantmen, the practice became widespread in the summer of 1917.

"It was really convoying that defeated the German plan to starve Great Britain," said Conrad. "It forced the submarines to attack when they could by using torpedoes. The submarines could not carry a lot of torpedoes and it was a long trip back from, say, the Irish Sea, to the submarine pens in Germany to refit. So one of the things the convoys with their destroyer escorts did is make the submarines stay under water. ... They were slower. It was difficult - the British were very good at reading German message traffic. ... They could figure out approximately where the German U-boats were operating. So they would reroute the convoys."

Indeed, convoys were a major naval success, not only in terms of shipping, but also when it came to the troop transports. In fact, the Navy got a 2 million-man Army to Europe without losing any troop ships. "The German high command did the calculations and they said, 'There are 2 million Americans now and there's more on the way, significantly more. We don't have the manpower to contend with more,'" explained Conrad. "The German high command looked at the numbers and said, 'We can't win,' and so they sued for peace."

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The Allies had another new technology they hoped to use against German U-boats as well. Shortly before World War I, in response to the Titanic disaster, a number of scientists patented underwater echo devices to help identify icebergs, technology that became very important with the advent of submarine warfare. Scientists, including a Canadian engineer named Reginald Fessenden, conducted a series of tests between 1912 and 1914, demonstrating depth sounding, underwater communications and echo ranging. Fessenden's hydrophone could tell how far away an object was, but not the exact direction. This flaw became increasingly evident as submarines became ever more of a threat, according to "The Submarine Review."

Early ultrasound technology corrected this problem, and the hydrophone claimed its first U-boat in 1916. "You had to stop your boat and put a microphone in the water and listen," said Conrad, "but they were working on the concepts of sonar." American research eventually made U-boats detectable up to 25 miles away, a distance that would increase exponentially during World War II.


In addition to submarines, another new platform used during World War I would go on to change warfare forever: aviation. But planes needed to interface with ships somehow, and in the first decade of the 20th century, the Navy explored various concepts, including catapults and specially built platforms. They hadn't been perfected yet, however; nor could manufacturers keep up with the demand for planes and the amount of new inventions and technological change. Naval aviators were limited geographically as a result, and, according to Conrad, naval planes were mostly used for sub spotting and short reconnaissance flights from the shore during the Great War. To be truly effective, pilots needed to be able to easily take off from and land on ships, and remain with those ships to quickly scramble to their defense.

After the war, in 1922, the U.S. Navy commissioned its first aircraft carrier, USS Langley (CV 1), which the service converted from the collier ship USS Jupiter (AC 3) by adding a flight deck topside, catapults and arresting wires, according to the Navy History and Heritage Command. By the end of the decade, the Navy had commissioned USS Lexington (CV 2) and USS Saratoga (CV 3). All three early carriers eventually served in World War II. Langley was scuttled after a Japanese bombing raid in February 1942 and Lexington sunk during the Battle of the Coral Sea in May 1942.

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"Through the 1920s and 1930s, naval thinkers showed a lot of imagination and innovation so when we had to fight World War II, we were probably in better shape," said Conrad. "The British made some wrong choices, and that's why ... particularly in the Pacific, you don't hear much about the British. ... Even though they had the first, they didn't pursue aircraft carriers. That was a mistake."

Ultimately, he said, "World War I is a time of invention and incubation and really the adult version comes with World War II."


Editor's note: Read more of All Hands magazine's coverage of the World War I centenary in "The Navy in the Great War" and "Women in a Man's Navy: First Women Enlist in 1917." Read about four key moments in the history of naval aviation in "Happy Birthday, Naval Aviation." For additional information about the U.S. Navy in World War I, check out the World War I page on the Naval History and Heritage Command website.