SMS Mainz SMS " Mainz " was a light cruiser of the German " Kaiserliche Marine " ( Imperial Navy ) during the First World War . She had three sister ships , , , and . She was built by the AG Vulcan shipyard in Stettin ; her hull was laid down in 1908 and she was launched in January 1909 . She was commissioned into the High Seas Fleet in October 1909 . She was armed with a main battery of twelve 10 . 5 cm SK L / 45 guns and had a top speed of . After her commissioning , she served with the II Scouting Group , part of the reconnaissance forces of the High Seas Fleet . She was assigned to patrols off the island of Heligoland at the outbreak of World War I in early August 1914 . At the Battle of Heligoland Bight on 28 August 1914 , the German patrol forces were attacked by superior British forces , including five battlecruiser s and several light cruisers . " Mainz " was initially stationed in support of the forces on the patrol line . She attempted to reinforce the beleaguered German forces , and encountered a much stronger force of British cruisers and destroyer s . They scored several damaging hits with gunfire and a torpedo that disabled " Mainz " and prompted her commander to abandon ship . The British rescued 348 men from the crew before the ship rolled over and sank . Eighty - nine men were killed in the battle , including her commanding officer . Design . " Mainz " was ordered under the contract name " Ersatz " and was laid down in 1907 at the AG Vulcan shipyard in Stettin . She was launched on 23 January 1909 and christened by the mayor of Mainz , Karl Emil Göttelmann , after which fitting - out work commenced . She was commissioned into the High Seas Fleet on 1 October 1909 . The ship was long overall and had a beam of and a draft of forward . She displaced at full combat load . Her propulsion system consisted of two sets of AEG - Curtiss steam turbines driving two propellers . They were designed to give . These were powered by fifteen coal - fired Marine water - tube boilers . These gave the ship a top speed of . " Mainz " carried of coal that gave her a range of approximately at . " Mainz " had a crew of eighteen officers and 349 enlisted men . The ship was armed with twelve 10 . 5 cm SK L / 45 guns guns in single pedestal mounts . Two were placed side by side forward on the forecastle , eight were located amidships , four on either side , and two were side by side aft . She also carried four 5 . 2 cm SK L / 55 anti - aircraft guns . She was also equipped with a pair of torpedo tube s submerged in the hull . She could also carry 100 mines . The conning tower had thick sides , and the deck was covered with up to thick armor plate . Service history . After her commissioning in 1909 , " Mainz " served with the reconnaissance forces of the German fleet . Her first commander was ( commander ) Friedrich Tiesmeyer , the uncle of Ernst Lindemann ; he held the command until January 1910 . She was assigned to the II Scouting Group , which screened for the battlecruiser s of the I Scouting Group . After the outbreak of World War I at the beginning of August 1914 , she and several other cruisers were tasked with patrol duties in the Heligoland Bight . The cruisers were divided with the torpedo boat flotillas , and assigned to rotate through nightly patrols into the North Sea . As part of this operation , " Mainz " conducted a patrol on the night of 16 August with the VIII Torpedo - boat Flotilla , without incident . At the same time , British submarine s began reconnoitering the German patrol lines . On 23 August , several British commanders submitted a plan to attack the patrol line with the light cruisers and destroyer s of the Harwich Force , commanded by Commodore Reginald Tyrwhitt . These ships would be supported by submarines and Vice Admiral David Beatty ' s battlecruiser s and associated light forces . The plan was approved and set for 28 August . The British forces began to leave port on the evening of 26 August , beginning with the submarines assigned to the operation . Most of the surface forces went to sea early on the following morning ; the 7th Cruiser Squadron , which had been added to provide further support to the Harwich Force , left port later in the day . On the morning of 28 August , " Mainz " was at anchor in the mouth of the Ems ; her sister , the flagship of Rear Admiral Leberecht Maass was re - coaling in Wilhelmshaven , lay in the entrance to the Weser . These three cruisers were assigned to support the cruisers and , and the aviso , which were stationed on the patrol line that morning . At 07 : 57 , the Harwich Force encountered the outer German torpedo boats , which fled back to the German cruisers . In the ensuing Battle of Heligoland Bight , " Stettin " engaged the British force first , and was quickly reinforced by " Frauenlob " . At 09 : 47 , " Mainz " was ordered to steam out behind the British to cut off their line of retreat . She got under way by 10 : 00 , and operated in conjunction with a floatplane used for reconnaissance . At around 12 : 30 , " Mainz " encountered the British cruiser and several destroyers . The ships engaged each other for the next forty - five minutes . Fifteen minutes into the engagement , three British cruisers appeared ; " Mainz " broke off the engagement and attempted to escape from the superior British forces . The pursuing British cruisers scored several hits , but by 12 : 55 , " Mainz " had escaped under cover of a dense smoke screen . Another British cruiser , , and six destroyers , appeared on " Mainz " s port side , however , and attacked the fleeing German ship . " Mainz " quickly scored hits on the destroyers , and ; " Laurel " was damaged and forced to withdraw and " Laertes " was disabled by a salvo that hit her engine room . A shell from one of the British cruisers hit " Mainz " at around 13 : 00 , which jammed her rudder at ten degrees to starboard . Her crew shut off the port engine in an attempt to correct the ship ' s course , but she continued to turn to starboard . By 13 : 20 , the majority of the ship ' s guns had been disabled and the ship ' s superstructure had been shot to pieces . Her center and aft funnel collapsed after suffering several hits . A torpedo from the destroyer then hit the ship on her port side , amidships ; this prompted the ship ' s commander to order the crew to abandon the stricken cruiser . He then left the conning tower with the navigation officer , both of whom were immediately killed by a shell hit . The ship ' s communication system was out of service , and so the order to abandon ship did not reach the entire crew . The ship ' s executive officer then reached the bridge , and reiterated the order to abandon the crippled ship at 13 : 35 . " Mainz " was by now completely disabled . Her engines were stopped and her guns had ceased firing . Shortly before 14 : 00 , came alongside and took off the wounded German sailors . At 14 : 10 , " Mainz " rolled over to port and quickly sank at the position 53°58 ' N and 6°42 ' W ; the survivors now in the water gave three cheers for their ship . The British rescued 348 survivors ; 89 men , including the ship ' s commander , were killed in the battle . Among the survivors was " Oberleutnant zur See " ( Sub - Lieutenant ) Wolfgang von Tirpitz , the son of Admiral Alfred von Tirpitz , the architect of the German fleet . Winston Churchill , then the First Lord of the Admiralty , informed Tirpitz via the US embassy in Berlin that his son survived the battle . In the course of the engagement , the British sank two more German cruisers : " Mainz " s sister " Cöln " and " Ariadne " , with minimal losses to themselves .