German commerce raiders in World War I

The German commerce raiders of World War I were those surface vessels used by the Imperial German Navy to pursue its war on Allied commerce, (the "Handelskrieg").
These comprised regular warships, principally cruisers, stationed in Germany's colonial empire, express liners commissioned as auxiliary cruisers and, later, freighters outfitted as merchant raiders. 
These vessels had a number of successes, and a significant impact on Allied naval strategy, particularly in the early months of the war.
The cruisers.
At the outbreak of World War I Germany had six light and two heavy cruisers, and four gunboats, stationed overseas. These ships were stationed at various ports in Germany's colonial empire, or at neutral ports protecting German interests.
In the west, she had "Karlsruhe" in the Caribbean and "Dresden" on the east coast of Mexico. 
In West Africa she had the gunboat "Eber"; in East Africa the cruiser "Konigsberg" and the gunboat "Geier". The largest force was in the Pacific, with the Far East Squadron under V Adm. Graf von Spee; two heavy cruisers, one light cruiser, and two gunboats, all at Tsingtau, and cruisers "Leipzig" and "Nurnberg" deployed at sea. 
With the commencement of hostilities these ships were ordered to attack Allied trade wherever they found it.
At the outbreak of war, von Spee was at sea and set out across the Pacific to harass and disrupt British and Allied shipping. He had with him "Scharnhorst", "Gneisenau" and "Emden" and was quickly joined by "Nurnberg" and two auxiliary cruisers. "Emden" was dispatched on a solo raiding voyage in the Indian Ocean, which was highly successful, while von Spee headed for Chile to secure supplies of coal. At Easter Island in October he was joined by "Leipzig" and "Dresden", and at Coronel in November he defeated a British squadron which was searching for him. In December however he was surprised in the act of attacking Port Stanley in the Falkland Islands, and his entire force, save one, was destroyed. 
Despite von Spee's skill and courage, his mission, to destroy Allied commerce where he found it, was a failure. Two British warships were sunk, and one sailing ship, by his squadron in the five months he remained at large, while his light cruisers on detachment, with one exception, also achieved little.
"Nurnberg" which had been on detached service, sent to relieve "Leipzig" had rejoined von Spee on the outbreak of war. She had encountered no Allied shipping and made no captures. After that her fate was linked with von Spee's and she was sunk at the Falklands.
"Leipzig" had been at Acapulco in Mexico. She originally headed north along the US coast, causing British commerce to come to a standstill. She was able to coal at San Francisco before heading south-west to join von Spee. In this time she took two ships, and in the South Pacific two more. Thereafter "Leipzig's" fate was also joined with von Spee's and she also was sunk at Falklands.
Another cruiser, "Dresden", also achieved little. On the east coast of Mexico at the outbreak of war, she moved down the coast of South America, looking for Allied shipping, but made just 2 captures before receiving orders to enter the Pacific and join von Spee's squadron. She did this in October 1914, making rendezvous at Easter island. In the Pacific "Dresden" took two more ships before von Spee's squadron was destroyed at the Battle of the Falkland Islands in December 1914. "Dresden" escaped, but was run to ground in March 1915 at Mas a Tierra island.
The exception was "Emden", which made one of the most successful raiding cruises of any German warship. 
After leaving von Spee at Pagan in August, "Emden", under FK Karl von Mueller, captured and disposed of sixteen Allied ships and two warships in a four-month career that ranged over the eastern Indian Ocean. "Emden" was finally brought to battle and destroyed on 9 November at Keeling Island by the Australia cruiser "Sydney".
On the other side of the Indian Ocean, in German East Africa, the IGN had the cruiser "Konigsberg" and the gunboat "Geier". 
"Konigsberg" set out one raiding voyage, to the Gulf of Aden, and sank one ship. In September she surprised the British cruiser "Pegasus" in Zanzibar harbour and sank her. But lack of coal limited her operations and fear of being herself caught in harbour made her captain opt for taking refuge in the river delta of the Rufiji. This hiding place was discovered in October and the channel successfully blocked in November. Thereafter, although "Konigsberg" remained a potential threat, and although the RN took another six months before she could be destroyed, from this point her raiding career was over.
"Geier" set out from East Africa in August, and crossed both the Indian and the Pacific oceans in search of Allied ships, but in three months was unsuccessful, capturing just one ship before interning herself at Honolulu.
In the west the most successful cruiser was "Karlsruhe", under FK Erich Kohler. After meeting and equipping the liner "Kronprinz Wilhelm", "Karlsruhe" set out on a raiding voyage along the South American trade routes. Using her attendant supply ships, and later, prizes, to scout for her, "Karlsruhe" moved through the ocean, her net cast wide, able to steam quickly to any target or to evade conflict. After two months she had captured and disposed of 16 ships, including one neutral Dutch freighter, and taken 500 prisoners. 
At the end of October these were dispatched to neutral Tenerife in one of the prizes, and "Karlsruhe" steamed north to open a new hunting ground in the Caribbean.
However, on 4 November 1914, 300 miles east of Barbados, "Karlsruhe" suffered a calamitous internal explosion, sinking her and killing her captain and 260 crew. 
The survivors were rescued by the supply ship "Rio Negro", which had been in attendance, and returned to Germany.
The Germans were able to keep the secret of her loss until March 1915; until that time "Karlsruhe" exerted an influence as a ghost ship on British naval strategy, forcing the Allies to guard against possible attacks.
The liners.
At the outbreak of war the Imperial German Navy had listed thirteen fast passenger liners for conversion into auxiliary cruisers, and another seven ships, express mail steamers, to serve as supply vessels. 
However the immediate imposition by the Royal Navy of a blockade of German ports caught the IGN unprepared; the ships in home ports were trapped there, while those ships that were at sea or in neutral ports, away from their outfits of stored armaments with neutral nations wary of allowing such conversion to take place in their facilities.
Of the six ships that were in home ports, the IGN converted three, though two ("Cap Polonio", as "Vineta", and "Victoria Louise") were deemed unsuitable and returned to their owners. Only "Kaiser Wilhelm der Grosse" carried out a raiding voyage. Three others ("Cap Finisterre", "Prinz Ludwig" and "Kaiserin August Victoria") were not taken up for conversion and remained in civilian hands.
Of the seven at sea, three were able to avoid British patrols and take up armaments from German warships. "Kronprinz Wilhelm" met "Karlsruhe" in the Atlantic, "Cap Trafalgar" met "Eber" from German West Africa off Brazil, and "Prinz Eitel Friedrich" sailed to Tsingtau where she was armed from "Luchs" and "Tiger". Four others, ("Kronprinzessin Cecilie", "Kaiser Wilhelm II", "George Washington", and "Prinz Friedrich Wilhelm") were unable to return to Germany or meet any German warship and were interned in neutral ports.
Two other ships, not originally foreseen but becoming available, were also converted to be auxiliaries. The liner "Berlin", which was at Bremerhaven undergoing repairs, was taken up as a minelayer and raider. In August "Emden" captured the Russian liner "Ryazan", earmarked by the Imperial Russian navy as an auxiliary, and sent her to Tsingtau for conversion. She served under the name "Cormoran".
These vessels, too, had mixed success. "Kaiser Wilhelm der Grosse" broke through the blockade to raid down the West African coast. After sinking three ships she was caught and sunk by the British cruiser . "Cap Trafalgar" was similarly caught and sunk by the AMC "Carmania", before making any captures. "Berlin" made one voyage, laying mines off Ireland which sank the British dreadnought "Audacious", before herself being interned in Norway. "Cormoran" was able to operate for three months in the Pacific and around the coast of Australia, but without a single success; she was forced into internment in Guam.
More successful was "Prinz Eitel Friedrich", which operated with "Cormoran" and v Spee's squadron before being detached after Coronel in November 1914. She then made a three-month voyage into the Atlantic, making eleven captures before being interned in March 1915 at Newport News in the United States.
The most successful of these auxiliaries was "Kronprinz Wilhelm", remaining at large for eight months and taking thirteen prizes before she too was interned in April 1915 at Newport News.
The freighters.
Following the collapse of the first phases of Germany's commerce war, the Imperial German Navy turned to the U-boat Arm as an alternative. Despite some successes, the inadequacies of the U-boat as a commerce raider quickly became apparent. Lacking the cruiser's speed and gun armament to overawe its victims, the U-boats were increasingly faced with ships that would resist capture by running, or, as more and more became defensively armed, by shooting back. 
Rather than accept defeat however, in February 1915 the IGN opted for a policy of unrestricted submarine warfare, a policy which inevitably led to deaths and destruction of civilians, neutrals and other non-combatants and created considerable political difficulties.
Another approach proposed was the outfitting of ordinary freighters as commerce raiders and, initially, minelayers. In contrast to the first auxiliaries these ships would be chosen for their endurance and range, relying on disguise rather than speed to escape destruction.
The first assay into this approach was "Meteor", which laid mines and attacked shipping in the White Sea during May and June 1915. A second voyage in August saw her involved in a gun-battle with a blockade ship, and she was later scuttled to avoid capture. 
In November 1915 the most successful of these raiders, the "Moewe", set out on her first voyage. In four months she accounted for 15 ships, totalling 50,000 GRT, and successfully returned to Germany unscathed. 
Two other attempts to emulate this failed however; In February 1916 "Wolf" was wrecked while setting out from Kiel, and the same month "Greif" was sunk when she was intercepted by the RN blockade. 
In August 1916 "Moewe" was out again, this time masquerading as "Vineta" in an attempt to confuse Allied intelligence, and taking a prize off Norway: In November she made a longer voyage to the South Atlantic which captured 25 ships. "Moewe" was able to extend her range by taking fuel and supplies from her prizes; she also outfitted one of them (commissioned as "Geier") to act as an auxiliary herself, and sent another back to Germany for conversion into a raider.
Also in November 1916 another raider, also called "Wolf", started a voyage of 15 months, to South Africa, the Indian Ocean and Australia, sinking 14 ships and laying mines that destroyed 15 more. "Wolf" was also able to extend her range with goods from her prizes, prolonging her voyage to a record-breaking 15 months. She too outfitted a prize (commissioned as "Iltis") to assist as an auxiliary minelayer.
In December 1916 the most unusual raider, "Seeadler", set out; a fully rigged sailing ship (though equipped with auxiliary motors) "Seeadler" sailed all the way to the South Pacific and sank 13 ships before being wrecked on a reef after eight months of operations
The last raider, "Leopard", (the prize sent in by "Moewe") set out in March 1917, but she too was intercepted by the RN blockade and in a fierce gun-battle was sunk with all hands.
With the return of "Moewe" that month, Germany's experiment with surface raiders was virtually ended, though "Wolf" remained at large for another year. 
In Feb 1917 Germany started another campaign of unrestricted submarine warfare, which, despite huge damage to Allied shipping, failed to defeat the Allies, but led to angry neutrals (most prominently the USA) joining the war against her.