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.
“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