SMS Frankfurt

Maps showing the maneuvers of the British (blue) and German (red) fleets on 30–31 May 1916

At the Battle of Jutland on 31 May – 1 June 1916, Frankfurt served as Boedicker's flagship, the commander of II Scouting Group. II Scouting Group was again screening for the I Scouting Group battlecruisers, again commanded by Vizeadmiral Franz von Hipper. Frankfurt was engaged in the first action of the battle, when the cruiser screens of the German and British battlecruiser squadrons encountered each other. Frankfurt, Pillau, and Elbing briefly fired on the British light cruisers at 16:17 until the British ships turned away. Half an hour later, the fast battleships of the 5th Battle Squadron had reached the scene and opened fire on Frankfurt and the other German cruisers, though the ships quickly fled under a smokescreen and were not hit.[6]

Shortly before 18:00, the British destroyers Onslow and Moresby attempted to attack the German battlecruisers. Heavy fire from Frankfurt and Pillau forced the British ships to break off the attack.[7] At around 18:30, Frankfurt and the rest of II Scouting Group encountered the cruiser HMS Chester; they opened fire and scored several hits on the ship. Rear Admiral Horace Hood's three battlecruisers intervened, however, and scored a hit on Wiesbaden that disabled the ship.[8] About an hour later, Canterbury scored four hits on Frankfurt in quick succession: two 6-inch (150 mm) hits in the area of Frankfurt's mainmast and a pair of 4-inch (100 mm) hits. One of the 4-inch shells hit forward, well above the waterline, and the second exploded in the water near the stern and damaged both screws.[9]

Frankfurt and Pillau spotted the cruiser Castor and several destroyers shortly before 23:00. They each fired a torpedo at the British cruiser before turning back toward the German line without using their searchlights or guns to avoid drawing the British toward the German battleships. Almost two hours later, Frankfurt encountered a pair of British destroyers and fired on them briefly until they retreated at full speed.[10] By 04:00 on 1 June, the German fleet had evaded the British fleet and reached Horns Reef.[11] Frankfurt had three men killed and eighteen wounded in the course of the engagement. She had fired 379 rounds of 15 cm ammunition and a pair of 8.8 cm shells, and launched a single torpedo.[12]

The ship participated in Operation Albion in October 1917, an operation to eliminate the Russian naval forces that still held the Gulf of Riga. The ship was part of II Scouting Group, commanded by Rear Admiral Ludwig von Reuter.[13] The following month, Frankfurt and the rest of II Scouting Group were engaged during the Second Battle of Heligoland Bight. Along with three other cruisers from II Scouting Group, Königsberg escorted minesweepers clearing paths in minefields laid by the British. The dreadnought battleships Kaiser and Kaiserin stood by in distant support.[14] During the battle, Frankfurt fired torpedoes at the attacking British cruisers, but failed to score any hits.[15] The British broke off the attack when the German battleships arrived on the scene, after which the Germans also withdrew.[16]

At 19:08 on 21 October 1918,[17] Frankfurt accidentally rammed and sank the U-boat UB-89 in Kiel-Holtenau, killing seven of her crew. Twenty-seven survivors were pulled from the water.[18] UB-89 was raised by the salvage tug Cyclop on 30 October but with the war almost over, she was not repaired and did not see further service.[17][19]

In the final weeks of the war, Scheer and Hipper intended to inflict as much damage as possible on the British navy, in order to secure a better bargaining position for Germany, whatever the cost to the fleet. On the morning of 29 October 1918, the order was given to sail from Wilhelmshaven the following day. Starting on the night of 29 October, sailors on Thüringen and then on several other battleships mutinied. The unrest ultimately forced Hipper and Scheer to cancel the operation. Most of the High Seas Fleet's ships, including Frankfurt, were interned in the British naval base in Scapa Flow, under the command of Reuter.[20]

Frankfurt (left) aground in Scapa Flow; salvage work in progress on the battleship Baden (right)

The fleet remained in captivity during the negotiations that ultimately produced the Versailles Treaty. Reuter believed that the British intended to seize the German ships on 21 June 1919, which was the deadline for Germany to have signed the peace treaty. Unaware that the deadline had been extended to the 23rd, Reuter ordered the ships to be sunk at the next opportunity. On the morning of 21 June, the British fleet left Scapa Flow to conduct training maneuvers, and at 11:20 Reuter transmitted the order to scuttle his ships.[21] British sailors boarded Frankfurt and beached her before she could sink.[22] She was raised the following month and thereafter transferred to the United States Navy as a war prize.[23]

She was formally taken over on 11 March 1920 in England and commissioned into the US Navy on 4 June.[24] As she had been damaged in the scuttling, she was taken under tow by the minesweepers Redwing, Rail, and Falcon and taken to Brest, France, where the ex-German battleship SMS Ostfriesland, which had also been ceded to the United States, took Frankfurt under tow. The three minesweepers then towed three ex-German torpedo boats in company with Ostfriesland and Frankfurt; the convoy then crossed the Atlantic to the New York Navy Yard. There, the ships were thoroughly inspected by naval engineers to determine the advantages and disadvantages of the German ships, with the goal of incorporating any lessons learned into future American designs. While there, she also had her watertight compartments completely sealed to improve her ability to remain afloat when damaged.[25][26]

In July 1921, the Army Air Service and the US Navy conducted a series of bombing tests off Cape Henry, Virginia, led by General Billy Mitchell. The targets included demobilized American and former German warships, including the old battleship Iowa, Frankfurt, and Ostfriesland. Frankfurt was scheduled for tests conducted on 18 July.[26] The attacks started with small 250-pound (110 kg) and 300 lb (140 kg) bombs, which caused minor hull damage. The bombers then changed over to larger 550 lb (250 kg) and 600 lb (270 kg) bombs; Army Air Service Martin MB-2 bombers hit Frankfurt with several of the 600 lb bombs and sank the ship at 18:25.[23][27]