Naval warfare in World War I was mainly characterised by blockade. The Allied powers, with their larger fleets and surrounding position, largely succeeded in their blockade of Germany and the other Central Powers, whilst the efforts of the Central Powers to break that blockade, or to establish an effective counter blockade with submarines and commerce raiders, were eventually unsuccessful. Major fleet actions were extremely rare and proved less decisive.

Prelude In the early 20th century, Britain and Germany engaged in a protracted naval arms race centred on the construction of dreadnought-type battleships. Germany’s effort to assemble a fleet capable of equalling the United Kingdom’s, then the world’s preeminent sea power and an island state dependent on maritime commerce, has frequently been identified as a principal source of the hostility that drew Britain into World War I. German leaders sought a navy commensurate with their nation’s military and economic stature to secure overseas trade routes and colonial holdings independently of British goodwill. Yet the prospect of such a fleet posed an inherent challenge to British naval dominance and the security of its global trade and empire.

After the First Moroccan Crisis (March 1905–May 1906) over Morocco’s colonial status, the major European powers entered a naval arms race that would define early twentieth-century geopolitics.

This competition drew heavily on the ideas of Captain Alfred Thayer Mahan, an American naval officer and maritime historian who, in 1887, published The Influence of Sea Power upon History. In it, Mahan contended that control of the world’s sea lanes had been the decisive factor behind the prosperity of maritime states. He demonstrated how Rome and Britain had attained global preeminence through naval supremacy, while powers such as Carthage under Hannibal and Napoleonic France had faltered for lack of a dominant fleet. Mahan argued that any nation aspiring to economic growth and imperial influence needed to replicate Britain’s model of concentrated sea-power and influence.

Naval arms race

Mahan's thesis was highly influential and led to an explosion of new naval construction worldwide. The US Congress immediately ordered the building of three battleships (with a fourth, , to be built two years later). Japan, whose British-trained navy wiped out the Russian fleet at the Battle of Tsushima, helped to reinforce the concept of naval power as the dominant factor in conflict. However, the book made the most impact in Germany. The German Kaiser, Wilhelm II, had been much impressed by the Royal Navy, when he visited his grandmother, Queen Victoria. His mother said that "Wilhelm's one idea is to have a Navy which shall be larger and stronger than the British navy". In 1898 came the first German Fleet Act, two years later a second doubled the number of ships to be built, to 19 battleships and 23 cruisers in the next 20 years. In another decade, Germany would go from a naval ranking lower than Austria to having the second largest battle fleet in the world. For the first time since Trafalgar, Britain had an aggressive and truly dangerous rival to worry about.

Mahan wrote in his book that not only world peace or the empire, but Britain's very survival depended on the Royal Navy ruling the waves. The Cambridge 1895 Latin essay prize was called "Britannici maris", or "British Sea Power". So when the great naval review of June 1897 for the Queen's diamond jubilee took place, it was in an atmosphere of unease and uncertainty. The question everyone wanted to know the answer to was how Britain was going to stay ahead. But Mahan could not give any answers. The man who thought he could was Jackie Fisher, commander in chief of the Mediterranean Fleet. He believed there were "Five strategic keys to the empire and world economic system: Gibraltar, Alexandria and Suez, Singapore, the Cape of Good Hope, and the Straits of Dover." His job was to keep hold of all of them.

Fisher's reforms

When he became First Sea Lord, Fisher began drawing up plans for a naval war against Germany. "Germany keeps her whole fleet always concentrated within a few hours of England," he wrote to the Prince of Wales in 1906. "We must therefore keep a fleet twice as powerful within a few hours of Germany." He therefore concentrated the bulk of the fleet in home waters, with a secondary concentration in the Mediterranean Fleet. He also had dozens of obsolete warships scrapped or hulked. The resources thus saved were directed to new designs of submarines, destroyers, light cruisers, battlecruisers and dreadnoughts. Fisher proclaimed, "We shall have ten Dreadnoughts at sea before a single foreign Dreadnought is launched, and we have thirty percent more cruisers than Germany and France put together."

German response

Admiral Alfred Tirpitz had often visited Portsmouth as a naval cadet and admired and envied the Royal Navy. Like the Kaiser, Tirpitz believed Germany's future dominant role in the world depended on a powerful navy. He demanded large numbers of battleships. Even when Dreadnought was launched, making his previously constructed 15 battleships obsolete, he believed that eventually Germany's technological and industrial might would allow Germany to out-build Britain ship for ship. Using the threat of his own resignation he forced the Reichstag to build three dreadnoughts and a battle cruiser. He also put aside money for a future submarine branch. At the rate that Tirpitz insisted upon, Germany would have thirteen in 1912, to Britain's 16.

When this was leaked out to the British people in spring 1909, there was public outcry. The people demanded eight new battleships instead of the four the government had planned for that year. As Winston Churchill put it, "The Admiralty had demanded six ships; the economists offered four; and we finally compromised on eight." Tirpitz had no option but to consider Britain's new dreadnought-building program as a direct threat to Germany. He had to respond, raising the stakes further. However, the commitment of funds to out-build the Germans meant Britain was abandoning any notion of a two-power standard for naval superiority. No amount of money would allow Britain to compete with Germany and Russia or the US, or even Italy. Thus a new policy, of dominance over the world's second leading sea power by a 60% margin, went into effect. Fisher's staff had been getting increasingly annoyed by the way he refused to tolerate any difference in opinion, and the eight dreadnought demand had been the last straw. Thus on January 25, 1910, Fisher left the Admiralty. Shortly after Fisher's resignation, Churchill became First Lord of the Admiralty. Under him, the race would continue; indeed Lloyd George nearly resigned when Churchill presented him with the naval budget of 1914 of 50 million pounds.

By the start of the war Germany had an impressive fleet both of capital ships and submarines. Other nations had smaller fleets, generally with a lower proportion of battleships and a larger proportion of smaller ships like destroyers and submarines. France, Italy, Russia, Austria-Hungary, Japan, and the United States all had modern fleets with at least some dreadnoughts and submarines.

Naval technology Naval technology in World War I was dominated by the newly created dreadnought battleship, with several large turrets of equally sized big guns. British ships generally had larger guns and were equipped and manned for quicker fire than their German counterparts, which usually had better optical equipment and rangefinding, and were much better compartmentalized and able to deal with damage. The British also generally had poor propellant handling procedures, a point that was to have disastrous consequences for the British battlecruisers at Jutland.

Many of the individual parts and systems of ships had recently improved dramatically. Oil was just being introduced to replace coal, containing as much as 40% more energy per volume, extending range and further improving internal layout. Another advantage was that oil gave off considerably less smoke, making visual detection more difficult. This was generally mitigated by the small number of ships so equipped, generally operating in concert with coal-fired ships.

The introduction of the turbine led to much higher performance, as well as freeing up room and thereby allowing for improved layouts. Whereas pre-dreadnought battleships were generally limited to , modern ships were capable of at least , and in the latest British classes, . The introduction of the gyroscope and centralized fire control, the "director" in British terms, led to dramatic improvements in gunnery. Ships built before 1900 had effective ranges of around , whereas the first "new" ships were good to at least , and modern designs to over .

A new class of ship, the battlecruiser, appeared just before the war. The British designs were armed like their heavier dreadnought cousins, but deliberately lacked armor to save weight in order to improve speed, so that these ships would be able to outgun anything smaller than themselves, and get away from anything larger. The German designs opted to trade slightly smaller main armament (11 or 12 inch guns compared to 12 or 13.5 inch guns in their British rivals) for speed, while keeping relatively heavy armor. They could operate independently in the open ocean where their speed gave them room to maneuver, or, alternately, as a fast scouting force in front of a larger fleet action.

The torpedo boat caused considerable worry for many naval planners. In theory, a large number of these inexpensive ships could attack in masses and overwhelm a dreadnought force. This led to the introduction of ships dedicated to keeping them away from the fleets, the "torpedo boat destroyers", or simply, "destroyers". Although the mass raid continued to be a possibility, another solution was found in the form of the submarine, increasingly in use.

The submarine could escape blockades that prevent the use of surface vessels. It could approach underwater, safe from the guns of both the capital ships and the destroyers (although not for long), and fire a torpedo salvo as deadly as a torpedo boat's. Limited range and speed, especially underwater, made these weapons difficult to use tactically. Submarines were generally more effective in attacking poorly defended merchant ships (in which case surfaced attacks through deck guns were favoured prior to 1917) than in fighting surface warships, though several small-to-medium British warships were lost to torpedoes launched from German U-boats.

Radio was in early use, with naval ships commonly equipped with radio telegraph, and merchant ships less so. Sonar was in its infancy by the end of the war. Aviation was primarily focused on reconnaissance, with the aircraft carrier being developed over the course of the war, and bomber aircraft capable of lifting only relatively light loads.

Naval mines were also increasingly well developed. Defensive mines along coasts made it much more difficult for capital ships to get close enough to conduct coastal bombardment or support attacks. The first battleship sinking in the war — that of — was the result of her striking a naval mine on 27 October 1914.Pemsel, Helmut A History of War at Sea, Naval Institute Press, 1977, page 160. Suitably placed mines also served to restrict the freedom of movement of submarines.

List of naval engagements

1914 Battle of Antivari First Battle of Heligoland Bight Battle of Penang Battle of Coronel Battle of the Falkland Islands 1915 Battle of Dogger Bank (1915) Gallipoli Campaign Battle of Más a Tierra 1916 Battle of Jutland Battle of Dogger Bank (1916) 1917

Second Battle of Heligoland Bight Battle of Moon Sound

1918 Battle of Imbros

Theaters

North Sea