North Sea The North Sea was the main theater of the war for surface action. The
British Grand Fleet took position against the German
High Seas Fleet. Britain's larger fleet could maintain a blockade of Germany, cutting it off from overseas trade and resources. Germany's fleet remained mostly in harbor behind their screen of mines, occasionally attempting to lure the British fleet into battle (one of such attempts was the
bombardment of Yarmouth and Lowestoft) in the hopes of weakening them enough to break the blockade or allow the High Seas Fleet to attack British shipping and trade. Britain strove to maintain the blockade and, if possible, to damage the German fleet enough to remove the threat to the islands and free the Grand Fleet for use elsewhere. In 1918 the U.S. Navy with British help laid the
North Sea Mine Barrage designed to keep U-boats from slipping into the Atlantic. Major battles included those at Heligoland Bight (in
1914 and again in
1917),
Dogger Bank (in 1915), and
Jutland (1916). Though British tactical success remains a subject of historical debate, Britain accomplished its strategic objective of maintaining the blockade and keeping the main body of the High Seas Fleet in port for the vast majority of the war. The High Seas Fleet remained a threat as a
fleet in being that forced Britain to retain a majority of its capital ships in the North Sea. The set-piece battles and maneuvering have drawn historians' attention; however, it was the naval blockade of food and raw material imports into Germany which ultimately starved the German people and industries and contributed to Germany seeking the
Armistice of 1918.
English Channel Although the English Channel was of vital importance to the
British Expeditionary Force (BEF) fighting in France, there were no big warships of the British Royal Navy in the channel. The primary threat to the British forces in the channel was the German High Seas Fleet based near Heligoland; the German fleet, if let out into the North Sea, could have destroyed any ship in the channel. The German High Seas Fleet could muster at least 13 dreadnoughts and many armored cruisers along with dozens of destroyers to attack the channel. The High Seas Fleet would be fighting against only six armored cruisers that were laid down in 1898–1899, far too old to accompany the big, fast dreadnoughts of the Grand Fleet based in Scapa Flow. The U-boat threat in the channel, although real, was not a significant worry to the Admiralty because they regarded submarines as useless. Even the German high command regarded the U-boats as "experimental vessels". Although the channel was a major artery of the BEF, it was never attacked directly by the High Seas Fleet.
Atlantic , painting by
Willy Stöwer Britain's maritime blockade significantly restricted Germany's access to vital resources, contributing to severe economic and material shortages. Conversely, the United Kingdom, reliant on seaborne imports due to its island geography, faced strategic vulnerabilities. While German U-boats were generally ineffective against naval warships, they had considerable success in disrupting commercial shipping by targeting merchant vessels, thereby threatening Britain’s supply chains. In 1915, Germany declared a naval blockade of Britain, to be enforced by its U-boats with unrestricted attacks on British ships. The U-boats sank hundreds of Allied merchant ships. However, submarines usually cannot rescue survivors, and may attack without giving warning or adequate time to abandon ship. Attacking civilian ships in this way violated the customary
cruiser rules and resulted in many civilian deaths, especially when passenger ships were sunk. Furthermore, the U-boats also sank neutral ships in the blockade area, either intentionally or because identification was difficult from underwater. This turned neutral opinion against the Central Powers, as countries like the U.S. and Brazil suffered casualties and losses to trade. Due to diplomatic and internal political pressure, the campaign was stopped that same year and instead for 1916 submarines attacked commerce under cruiser rules, to moderate success. In early 1917, Germany declared unrestricted submarine warfare once more, including attacks without warning against all ships in the "war zone", including neutrals. This was a major cause of U.S. declaration of war on Germany. While the U-boat campaign sank many merchant ships, it ultimately did not have a significant economic impact on Britain, failing to be a war-winning wonder weapon as German naval authorities had hoped, and British authorities feared. Far from being starved into submission, and in stark contrast to the experience of Germany, British civilian nutrition improved, with a rise in the average consumption of meat. The U-boats were countered by a variety of measures - expanded shipbuilding and requisitioning of neutral and war ships, minefields to block U-boat access,
defensive armaments on merchant ships (preventing the more effective U-boat tactic of surface attacks with deck guns) and eventually by grouping merchant ships into
defended convoys. This was also assisted by the U.S. entry into the war and the increasing use of primitive sonar and aerial patrolling to detect and track submarines.
Mediterranean Some limited sea combat took place between the navies of Austria-Hungary and Germany and the Allied navies of France, Britain, Italy and Japan.
Aegean The navy of the
Ottoman Empire only sortied out of the Dardanelles once late in the war during the
Battle of Imbros, preferring to focus its operations in the
Black Sea. Unlike in the Atlantic, the Aegean saw large scale combat involving the French Navy, which provided most of the support vessels to aid in the invasion of Dardanelles and bombarded Athens in an attempt to secure Greek ascension to the Entente. The main fleet action came in 1915 when the Triple Entente attempted to knock the Ottoman Empire out of the war entirely by capturing
Constantinople and securing allied control over the Dardanelles. This operation turned into the
Battle of Gallipoli and ended in defeat for the Triple Entente,
Winston Churchill was subsequently force to resign as
First Lord of the Admiralty as a result.
Black Sea The Black Sea was mainly the domain of the Russians and the Ottoman Empire. The large Russian fleet was based in
Sevastopol and it was led by two diligent commanders: Admiral
Andrei Eberhardt (1914–1916) and Admiral
Alexander Kolchak (1916–1917). The Ottoman fleet on the other hand was in a period of transition with many obsolete ships. It had been expecting to receive two powerful dreadnoughts fitting out in Britain, but the UK seized the completed and with the outbreak of war with Germany and incorporated them into the Royal Navy. The war in the Black Sea started when the Ottoman Fleet
bombarded several Russian cities in October 1914. The most advanced ships in the Ottoman fleet consisted of two ships of the German Mediterranean Fleet: the powerful battlecruiser and the speedy light cruiser , both under the command of the skilled German Admiral
Wilhelm Souchon.
Goeben was a modern design, and with her well-drilled crew, could easily outfight or outrun any single ship in the Russian fleet. However, even though the opposing Russian battleships were slower, they were often able to amass in superior numbers to outgun
Goeben, forcing her to flee. A continual series of cat and mouse
operations ensued for the first two years with both sides' admirals trying to capitalize on their particular tactical strengths in a surprise ambush. Numerous battles between the fleets were fought in the initial years, and
Goeben and Russian units were damaged on several occasions. The Russian Black Sea fleet was mainly used to support General
Nikolai Yudenich in his
Caucasus Campaign. However, the appearance of
Goeben could dramatically change the situation, so all activities, even shore bombardment, had to be conducted by almost the entire Russian Black Sea Fleet, since a smaller force could fall victim to
Goebens speed and guns. However, by 1916, this situation had swung in the Russians' favor –
Goeben had been in constant service for the past two years. Due to a lack of facilities, the ship was not able to enter refit and began to suffer chronic engine breakdowns. Meanwhile, the Russian Navy had received the modern dreadnought which although slower, would be able to stand up to and outfight
Goeben. Although the two ships
skirmished briefly, neither managed to capitalize on their tactical advantage and the battle ended with
Goeben fleeing and
Imperatritsa Mariya gamely trying to pursue. However, the Russian ship's arrival severely curtailed
Goebens activities and so by this time, the Russian fleet had nearly complete control of the sea, exacerbated by the addition of another dreadnought, . German and Turkish light forces, however, continued to raid and harass Russian shipping until the end of the war in the east. After Admiral Kolchak took command in August 1916, he planned to invigorate the Russian Black Seas Fleet with a series of aggressive actions. The Russian fleet mined the exit from the
Bosporus, preventing nearly all Ottoman ships from entering the Black Sea. Later that year, the naval approaches to
Varna, Bulgaria, were also mined. The greatest loss suffered by the Russian Black Sea fleet was the destruction of
Imperatritsa Mariya, which blew up in port on October 20 (October 7 o.s.) 1916, just one year after being commissioned. The subsequent investigation determined that the explosion was probably accidental, though sabotage could not be completely ruled out. The event shook Russian public opinion. The Russians continued work on two additional dreadnoughts under construction, and the balance of power remained in Russian hands until the collapse of Russian resistance in November 1917. To support the Anglo-French attack on the Dardanelles, British, French and Australian submarines were sent into the Black Sea in the spring of 1915. A number of Turkish supply ships and warships were sunk, while several submarines were lost. The boats were withdrawn at the evacuation of the Dardanelles in January 1916. The small Romanian Black Sea Fleet defended the port of
Sulina throughout the second half of 1916, causing the sinking of one German submarine. Its minelayer also defended the Danube Delta from inland, leading to the sinking of one Austro-Hungarian Danube monitor. (See also
Romanian Black Sea Fleet during World War I) Despite losing most of their coastline to the
Central Powers after the
Second Battle of Cobadin in October 1916, the Romanians still managed to keep the mouths of the Danube and the
Danube Delta under their control, due to the combined actions of their riverine flotilla of four monitors and the protected cruiser
Elisabeta, based at Sulina. The Romanian Navy repelled two attacks of the Imperial German Navy on the port of Sulina. The first attack took place on 30 September 1916, when the Romanian torpedo boat
Smeul engaged the German submarine
UB-42 near Sulina, damaging her periscope and conning tower and forcing her to retreat. The second attack took place on 7 November, when German
Friedrichshafen FF.33 seaplanes bombarded Sulina but two of them were shot down into the sea by Romanian anti-aircraft defenses (including the cruiser
Elisabeta) and were subsequently captured by Romanian motorboats. In mid-November 1916,
UC-15, the only minelaying submarine of the Central Powers in the Black Sea, was sent to lay 12 mines off Sulina and never returned, being most likely sunk by her own mines along with all of her crew. She could have also been sunk by the barrage of 30 mines laid at Sulina by the Romanian minelayer
Alexandru cel Bun. When Bulgaria entered World War I in 1915, its navy consisted mainly of a French-built torpedo gunboat called
Nadezhda and six torpedo boats. It mostly engaged in mine warfare actions in the Black Sea against the Russian Black Sea Fleet and allowed the Germans to station two U-boats at Varna, one of which came under Bulgarian control in 1916 as
Podvodnik No. 18. Russian mines sank one Bulgarian torpedo boat and damaged one more during the war.
Baltic Sea In the
Baltic Sea, Germany and Russia were the main combatants, with
a number of British submarines sailing through the
Kattegat to assist the Russians. With the German fleet larger and more modern (many High Seas Fleet ships could easily be deployed to the Baltic when the North Sea was quiet), the Russians played a mainly defensive role, at most attacking convoys between Germany and Sweden. A major coup for the Allied forces occurred on August 26, 1914 when as part of a reconnaissance squadron, the
light cruiser ran aground in heavy fog in the
Gulf of Finland. The other German ships tried to refloat her, but decided to scuttle her instead when they became aware of an approaching Russian intercept force. Russian Navy divers scoured the wreck and successfully recovered the German naval
codebook which was later passed on to their British Allies and contributed immeasurably to Allied success in the North Sea. With heavy defensive and offensive mining on both sides, fleets played a limited role in the Eastern Front. The Germans mounted major naval attacks on the
Gulf of Riga,
unsuccessfully in August 1915 and
successfully in October 1917, when they occupied the islands in the Gulf and damaged Russian ships departing from the city of
Riga, recently captured by Germany. This second operation culminated in the one major Baltic action, the
battle of Moon Sound at which the Russian battleship was sunk. By March 1918, the
Russian Revolution and the
Treaty of Brest-Litovsk made the Baltic a German lake, and German fleets transferred troops to support the
White side in the
Finnish Civil War and to occupy much of Russia, halting only when defeated in the west.
Asia and the Pacific A number of German ships stationed overseas at the start of the war engaged in raiding operations in poorly defended seas, such as , which raided into the
Indian Ocean, sinking or capturing thirty Allied merchant ships and warships, bombarding
Madras and
Penang, and destroying a radio relay on the
Cocos Islands before being sunk there by . Better known was the German
East Asia Squadron, commanded by Admiral Graf
Maximilian von Spee, who sailed across the Pacific,
raiding Papeete and winning the
Battle of Coronel before being defeated and mostly destroyed at the
Battle of the Falkland Islands. The last remnants of Spee's squadron were interned at Chilean ports and destroyed at the
Battle of Más a Tierra. Allied naval forces captured many of the isolated German colonies, with
Samoa,
Micronesia,
Qingdao,
German New Guinea,
Togo, and
Cameroon falling in the first year of the war. As Austria-Hungary refused to withdraw its cruiser from the German naval base of Qingdao, Japan declared war in 1914 not only on Germany, but also on Austria-Hungary. The cruiser participated in the
defense of Qingdao where it was sunk in November 1914.
Africa Despite the loss of the last German cruiser in the Indian Ocean, , off the coast of
German East Africa in July 1915, German East Africa held out in a long guerilla land
campaign.
British naval units despatched through Africa under Lieutenant-Commander
Geoffrey Spicer-Simson had won strategic control of
Lake Tanganyika in a
series of engagements by February 1916, though fighting on land in German East Africa continued until 1918. ==Fleets overview==