In 1914 both Britain and Germany armed merchantmen. British armed merchant cruisers were intended to protect trade and to enforce the blockade of Germany. The German equivalents were commerce raiders.
The only commerce raider to leave a German port and slip out past the British blockade in August 1914 was the Norddeutscher Lloyd Line’s 14,000 ton Kaiser Wilhelm der Grosse, commanded by Kapitän Max Reymann. The other early German merchant cruisers were abroad at the start of the war and were armed by German warships.
She was capable of 22.5 knots and on her maiden voyage in 1897 won the Blue Riband for the fastest crossing of the Atlantic. As a merchant cruiser she was armed with six 105mm (4.1 inch) and two 37mm (1.5 inch) guns. Her main weakness was her high coal consumption.
On 7 August, three days after leaving Hamburg, the Kaiser Wilhelm captured and sank the steam trawler Tubal Cain, whose crew were taken on board the German ship.
A week later the Kaiser Wilhelm picked up a signal from the British liner Galician, which was concerned about the threat of German commerce cruisers near Tenerife. The German ship sent her a reassuring message and then intercepted her on the afternoon of 15 August.
The Galician was carrying a general cargo and nine first class and 30 second class passengers. Reymann had her wireless disabled and took off two of her passengers, Lieutenant J Deane of the First Battalion East Lancashire Regiment and Gunner C Shurmer of the Royal Garrison Artillery. At 5 am on 16 August Reymann allowed the Galician to go with the following signal: ‘I will not destroy your ship on account of the women and children on board. You are dismissed. Good-bye.’ Click here for a film reconstruction of the incident.
On 16 August Kaiser Wilhelm intercepted three British merchantmen. The Kaipara and Nyanga were sunk after the 101 men on board them had been transferred to the German ship. The third ship, the modern Royal Mail steamer Arlanza, had women and children amongst her passengers. Reymann allowed her to go after she threw her wireless overboard.
The Galician made Tenerife on 16 August and informed the Admiralty of the presence of the German raider. The Galician was able to rig up an emergency wireless with help of some spare parts obtained at Tenerife. The Arlanza was also able to set up a replacement wireless. Both ships used their temporary radios cautiously, listening for enemy signals rather than transmitting their own.
The Arlanza reached Las Palmas on 17 August and sent a report to the Admiralty. Just outside the port she told the armoured cruiser HMS Cornwall what had happened. This affair shows that commerce raiders were putting themselves at risk if they released enemy merchantmen and that it was hard to silence a radio equipped ship permanently.
The protected cruiser HMS Highflyer, captained by Henry Buller, was sent on 24 August to investigate a report that the Kaiser Wilhelm had been at Rio de Oro, a remote anchorage on the coast of Spanish Sahara, a week earlier. She was still there when Highflyer arrived on 26 August, re-coaling and re-provisioning from the merchant ships Arucas, Magdeburg and Bethania. A fourth merchantman, the Duala, had returned to Las Palmas.
The Kaiser Wilhelm was hopelessly outgunned by Highflyer’s 11 6 inch guns, nine 12 pounders, six 3 pounders and two 18 inch torpedo tubes. She was faster than the British ship’s 20 knots, but could not flee as she did not have steam up.
The three merchant ships fled; Reymann had transferred his prisoners to the Arucas, who were released when she reached Las Palmas on 28 August. The Bethania was heading for Charleston in the USA with 450 of Kaiser Wilhelm’s crew, but she was captured by HMS Essex on 7 September.
After an hour and a half the Germans scuttled and abandoned their ship. The British Official History states that Buller left them because they took up ‘a menacing position behind the sandhill.’ British casualties were one man killed and five wounded. The damage to Highflyer was too minor for her to need dockyard repair. This website says that Reymann worked his passage back to Germany as a stoker on a neutral vessel.
Both sides breached Spanish neutrality in this action, the Germans by using the harbour as a base and the British by attacking them; the Spanish protested to both. The Admiralty concluded that Captain Buller was correct in attacking, since not doing so would have invited commerce raiders to use other remote anchorages in neutral countries that lacked the naval strength to enforce their neutrality. Spain accepted the British apology.
The Kaiser Wilhelm der Grosse’s cruise was notable mainly for Reymann’s chivalry. His ship sank only three merchant ships with a total tonnage of 10,685 tons; the ships and their cargoes were worth under £400,000. Later in the war, the Germans would find that innocuous looking freighters were better commerce raiders than fast liners with a high coal consumption.
 C. E. Fayle, Seaborne Trade., 3 vols. (London: HMSO, 1920). i, p. 79.
 J. S. Corbett, H. Newbolt, Naval Operations, 5 vols. (London: HMSO, 1938)., i, p. 136, footnote.
 Ibid. i, p. 185
 Figures from Fayle, Seaborne. i, p. 82.