SMS Von der Tann was the first battlecruiser built for the German Kaiserliche Marine, as well as Germany’s first major turbine-powered warship. At the time of her construction, Von der Tann was the fastest dreadnought-type warship afloat, capable of reaching speeds in excess of 27 knots (50 km/h; 31 mph). She was designed in response to the British Invincible class. While the German design had slightly lighter guns — 28 cm (11 in), compared to the 30.5 cm (12 in) Mark X mounted on the British ships—Von der Tann was faster and significantly better-armoured. She set the precedent of German battlecruisers carrying much heavier armour than their British equivalents, albeit at the cost of smaller guns.

Design of Von der Tann began in August 1906, under the name “Cruiser F”, amid disagreements over the intended role of the new ship. Admiral Tirpitz advocated a ship similar to the new British battlecruisers of the Invincible class: heavier guns, lighter armour, and higher speed with the intention of using the ship as a fleet scout and to destroy the opposing fleet’s cruisers.

On 22 June 1907, the Kaiser authorized construction of Cruiser F, to be named Von der Tann, after Ludwig Freiherr von und zu der Tann-Rathsamhausen, a Bavarian general who fought in the Franco-Prussian War of 1870. The contract was awarded to the Blohm & Voss shipyard in Hamburg, on 26 September 1907. The keel was laid on 21 March 1908, and the ship was launched nearly a year later, on 20 March 1909. The ship cost 36.523 million Marks.

Von der Tann carried eight 28 cm (11.02 in) SK L/45 guns, mounted in four twin turrets: one fore, one aft, and two staggered wing turrets. The guns were emplaced in the Drh. L C/1907 turntable mount, which was traversed electrically, while the guns themselves used hydraulics to change elevation. The guns could be elevated up to 20 degrees, which enabled a maximum range of 18,900 m (20,700 yd).  The main guns fired a 302 kg (670 lb) armour-piercing shell that had a muzzle velocity of 875 m/s. A total of 660 projectiles were stored in four shell rooms, each containing 165 shells. The wing turrets were staggered in such a way that all eight guns were able to fire on broadside on a very wide arc.

Unlike her British contemporaries, Von der Tann also carried a heavy secondary battery, consisting of ten 15 cm (5.91 in) SK L/45 guns, casemated in MPL C/06 pivot mounts, each with 150 high explosive and armour-piercing shells. At construction, these guns could fire their 45.3 kg (100 lb) shells at targets up to 13,500 m (14,800 yd). She was also armed with sixteen 8.8 cm SK L/45 naval gun 8.8 cm (3.46 in) SK L/45 guns, to defend against torpedo boats and destroyers.

Image and text courtesy Wikipedia

SMS Derfflinger

Built by Blohm & Voss at their yard in Hamburg, Derfflinger ’​s keel was laid in January 1912. She was to have been launched on 14 June 1913, but the wooden sledges upon which the ship rested became jammed; the ship moved only 30–40 centimeters. A second attempt was successful on 12 July 1913. A crew composed of dockyard workers took the ship around the Skagen to Kiel. In late October, the vessel was assigned to the I Scouting Group, but damage to the ship’s turbines during trials prevented her from joining the unit until 16 November.

On completion she displaced nearly 27,000 t (27,000 long tons; 30,000 short tons) and was 210 m (690 ft) long. The ship had a crew of 44 officers and 1,068 enlisted men. Derfflinger was equipped with two sets of high- and low-pressure turbines powered by 14 coal-burning boilers that drove four propellers. She was capable of a top speed of 26.4 kn (48.9 km/h; 30.4 mph), and could steam for 5,600 nautical miles (10,400 km; 6,400 mi) at a cruising speed of 14 kn (26 km/h; 16 mph). In early August 1915, a derrick was mounted amidships, and tests with Hansa-Brandenburg W seaplanes were conducted.

Mounting a main armament of eight 30.5 cm (12 in) guns, Derfflinger was the largest and most powerful German battlecruiser at the time. The ship’s armament was rounded out by twelve 15 cm (5.9 in) guns in single casemate mounts and eight 8.8 cm (3.45 in) guns, also placed in casemates, though four of these were removed in 1916. An additional four 8.8 cm flak guns were installed amidships. Four 50 cm (20 in) submerged torpedo tubes were carried; one was located in the bow, two on the broadside, and one in the stern.

(Source: Wikimedia)

“Derfflinger firing full salvo” by Unknown – http://www.flickr.com/photos/21298246@N04/2625228815/; this was scanned from Hase, Georg von (1920). Skagerrak, die Grösste Seeschlacht der Weltgeschichte (in German). Leipzig, Germany: Hase & Koehler. p. 102. Retrieved 2009-07-31.. Licensed under PD-US via Wikipedia – http://en.wikipedia.org/wiki/File:Derfflinger_firing_full_salvo.jpg#mediaviewer/File:Derfflinger_firing_full_salvo.jpg

“Derfflinger class battlecruiser – Jane’s Fighting Ships, 1919 – Project Gutenberg etext 24797” by William Oliver Stevens and Allan Westcott. credited to Jane’s Fighting Ships, 1919 – A History of Sea Power, by William Oliver Stevens and Allan Westcott. Project Gutenberg etext 24797. Licensed under Public Domain via Wikimedia Commons – http://commons.wikimedia.org/wiki/File:Derfflinger_class_battlecruiser_-_Jane%27s_Fighting_Ships,_1919_-_Project_Gutenberg_etext_24797.png#mediaviewer/File:Derfflinger_class_battlecruiser_-_Jane%27s_Fighting_Ships,_1919_-_Project_Gutenberg_etext_24797.png

By the start of the First World War, the German Imperial Navy possessed 22 pre-Dreadnoughts, 14 dreadnought battleships and 4 battle-cruisers. A further three ships of the König class were completed between August and November 1914, and two Bayern-class battleships entered service in 1916. The battlecruisers Derfflinger, Lützow, and Hindenburg were completed in September 1914, March 1916, and May 1917, respectively.

Admiral von Tirpitz became the commander of the Navy. The main fighting forces of the navy were to become the High Seas Fleet, and the U-boat fleet. Smaller fleets were deployed to the German overseas protectorates, the most prominent being assigned to the East Asia Station at Tsingtao.

The German Navy’s U-boats were also instrumental in the sinking of the passenger liner and auxiliary cruiser, the RMS Lusitania, on 7 May 1915, which was one of the main events that led to the USA joining the war two years later in 1917.

Notable battles fought by the Navy were (up to the East Coast Raid of December 1914):

• Battle of Heligoland Bight (Rear Admiral Leberecht Maass) – 1914.
• Battle of Coronel (Vice Admiral Maximilian von Spee) – 1914. The German East Asia Squadron defeated the British West Indies Squadron.
• Battle of the Falkland Islands (Vice Admiral Maximilian von Spee) – 1914. The East Asia Squadron was defeated by a British battlecruisers.

You can read a much more detailed history on Wikipedia.

Battlecruisers of Germany