The action of 10 May 1915, or Battle of the Bosporus, was a naval encounter between the Russian pre-dreadnought squadron and the Ottoman battlecruiser Yavuz Sultan Selim in the Black Sea, north of the Bosporus. After a brief exchange of fire the Ottomans withdrew. The battle took place during the main operation of the Black Sea Fleet aimed at shelling the Bosporus fortifications. The action of the battlecruiser led to the interruption of the operation, but it did not manage to inflict significant damage to the Russian fleet, suffering only minor damage itself.
Background After the outbreak of hostilities between Russia and the Ottoman Empire on 29 October 1914, naval operations in the Black Sea primarily involved shelling coastal targets and laying mines. The core of the Russian fleet in this area consisted of five outdated battleships of the pre-dreadnought generation, each armed with four 305 mm guns, except for the weaker Rostislav with 254 mm guns. The main adversary of the Russian Black Sea Fleet was the German battlecruiser Goeben, which, after breaking through to Constantinople along with the cruiser Breslau, was formally incorporated into the Ottoman navy as Yavuz Sultan Selim, although it was still known in practice by its original name. It significantly surpassed each of the Russian ships existing at the beginning of the war in terms of speed, armor and artillery, which included 10 guns of 28 cm caliber,The Germans specified the caliber of the guns in centimeters; the actual caliber was 283 mm. () with a higher rate of fire than the Russian heavy guns. This forced the Russians to operate in groups consisting of at least three battleships to equalize the odds in artillery combat. Additionally, due to the older construction of the Russian battleships, each hit could have serious consequences for them, especially in long-range duels, when steeply falling shells could penetrate the deck. The first inconclusive battle between the Black Sea Fleet and the Yavuz Sultan Selim occurred on 18 November 1914, near Cape Sarych, in which both sides' ships suffered damage.
Parallel to the start of the Dardanelles Campaign by the Western Entente powers, the Russian command ordered demonstrative actions to divert the attention of the Ottomans, including shelling positions and a possible local landing in the Bosporus area. To this end, on 28 March, 25 April, 2 May, and 3 May 1915, the Black Sea Fleet shelled Ottoman fortifications north of the Bosporus, also using seaplanes carried by base ships in the action.According to , the last shelling of the Bosporus took place on May 1st and 2nd; there is no information there about shelling on April 25th. However, these actions did not lead to significant damage. On May 6, Russian ships returned to the base in Sevastopol after the final raid, during which 10 Ottoman ships (including 4 steamers) were sunk, seriously disrupting Ottoman coal transport, and an Italian ship carrying contraband was seized.On May 1–5, 1915, the steamers Necat (1523 BRT), Yeşilirmak (865 BRT), Güzel Girit (1232 BRT), Morna (1495 BRT) were sunk, and the Amalia (413 BRT) was captured. () On the same day (May 6), the best ships available to the Ottomans were sent on a raid into the Black Sea: Yavuz Sultan Selim and the cruisers Midilli and Hamidiye. On the morning of May 8, Yavuz Sultan Selim sailed along the coast of Crimea, but there were no encounters with the Russian fleet or shipping, nor was there any shelling of the coast due to limited ammunition supplies. The Ottoman ships then returned to port by evening.
Around noon on May 8, the main Russian ships left Sevastopol but encountered no enemy. Therefore, the main forces of the Black Sea Fleet set out in the afternoon for another operation to shell Ottoman positions and raid with light forces in the Ottoman coal basin around Zonguldak. The Russian squadron consisted of 5 battleships, 2 protected cruisers, an unarmored aircraft cruiser (Almaz), 15 destroyers (7 of them modern, with turbine propulsion), 6 naval trawlers (converted steamships), and the seaplane carrier Imperator Aleksandr I with 5 seaplanes (3 Curtiss and 2 M-5).
On 9 May 1915, a Russian squadron (including the cruiser Kagul and the destroyer Biespokojnyj) attacked Ottoman shipping between Kozlu and Eregli, sinking four steamers and many sailing ships. The cruiser Pamiat' Mierkurija and the destroyer Dierzkij shelled the port of Ereğli, causing fires and sinking one ship.During the raid on May 9, the ship Selanik (with 1127 GT) was heavily damaged, and it remained unrepaired for the rest of the war. Additionally, the ship Sadiç (763 GT) was damaged, and while attempting to escape, it ran aground. In the port of Ereğli, the ship Millet (812 GT) was sunk. (, ) The Russians also attempted to land a sabotage group from a motorboat towed by a boat to cause damage in the port, but they had to retreat (without casualties) due to rifle fire.
The battlecruiser Yavuz Sultan Selim, under Captain Richard Ackermann, immediately put to sea in order to intercept the Russians. Early on the morning of 10 May, a bombardment force detached from the Russian squadron in order to attack the Bosphorus forts. This consisted of the obsolete pre-dreadnoughts and Panteleimon, the seaplane carriers Almaz and Imperator Alexander I, as well as a screen of destroyers and minesweepers.
After receiving reports of the shelling of Ereğli, the battleship Yavuz Sultan Selim was ordered to take action against the Russian group and left the Bosporus in the afternoon. However, by that time, the Russian ships had already left Ereğli. At 2:38 P.M., Yavuz Sultan Selim spotted the Russian submarine Tiulen on the surface and turned back, pretending to return towards the Bosporus, causing the submarine to not report the presence of the battleship. Before entering the strait, Yavuz Sultan Selim headed east, remaining in the Black Sea to locate the Russian main forces the next day and, if possible, surprise them while they were separated.
Battle
On May 10, at dawn, the Russian ships were about 22 miles from the Bosporus. The bombardment group consisted of the older battleship Tri Sviateitelia (under the command flag of Rear Admiral N. Putiatin, commander of the 2nd Brigade of Line Ships) and the newer Pantelimon, which replaced the weaker Rostislav due to its longer-range guns. At 5:40 A.M., the group headed towards the shore, following the minesweepers tasked with clearing the minefields, escorted by six older destroyers from the 4th and 5th Destroyer Divisions, which were also towing minesweeping gear, and two newer destroyers from the 1st Destroyer Division. The battleships Evstafi, Ioann Zlatoust, and Rostislav, along with the remaining destroyers, formed a covering group, protecting the bombardment group from the seaward side. The cruisers Kagul and Pamiat' Merkuria were sent to watch to the west and east, respectively; the latter sank a small Ottoman sailing ship carrying coal. A Curtiss seaplane was also launched into the air.
The Ottoman destroyer , acting as a guard ship at the mouth of the Bosphorus, sighted the bombardment force at 5:40 A.M. and radioed a warning to Yavuz. Captain Ackermann promptly set his ship on a course to intercept at . Approaching from the east at high speed, the destroyer was detected before 7:00 A.M. by the vigilant cruiser Pamiat' Merkuria and a seaplane, which alerted the main forces. The Russian cruiser returned to the group at maximum speed to evade the faster Yavuz Sultan Selim.A humorous touch could be considered that the German ship signaled its call signs with a signal lamp: GB (Goeben). () Upon receiving information about the opponent, the main Russian commander, Admiral Eberhardt, directed the battleships of the covering force to the south to approach the bombardment group. Simultaneously, orders to return were given for the detached battleships, which had already moved about 15 nautical miles away.
The destroyer proceeded to engage at 7:10 A.M., firing on the minesweepers from a distance of 4.1 nautical miles. The battleships Evstafi, Ioann Zlatoust, and Rostislav engaged in battle in line-ahead formation, while Yavuz Sultan Selim changed course to parallel them, sailing on their starboard side. At 7:51 A.M., Ioann Zlatoust and Yavuz Sultan Selim opened fire on each other from a distance of 9.4 nautical miles, followed by the flagship battleship Evstafi. According to procedures developed in the fleet, Ioann Zlatoust directed the centralized fire of both battleships. Both groups exchanged fire, but initially without effect. Subsequent five-gun salvos began to surround the flagship Evstafi, flooding the rangefinders with water spouts and damaging the splinter shields and wooden elements, although no direct hits were achieved. Initially, the Russian salvos were too short, but the water spouts they caused somewhat hindered the Germans' aim. Rostislav (commanded by Captain of 1st Rank Kazimierz Porębski) did not participate in the bombardment to avoid interfering with the correction of fire for the 305mm guns of the stronger battleships. The commander of the Russian group and the entire Black Sea Fleet, Admiral Andrei Eberhardtt, skillfully maneuvered, making course and speed adjustments to make it difficult for the enemy to target. In particular, instead of increasing the speed of the column after the Germans obtained cover, he reduced it from 10 to 9 knots, causing the next salvo to fall short of Evstafi. He also facilitated the approach of the remaining battleships.
At 07:53 hours, Eberhardt's force met Yavuz sailing along a parallel course. Ackermann believed this to be the bombardment detail, though he was confused as to why he was facing three battleships instead of two. He soon realized his mistake when Tri Sviatitelia and Panteleimon joined the Russian battle line. The Ottoman battlecruiser fired 160 shells in the ensuing engagement, but scored no hits and caused no damage. One near miss on Evstafi sent a cascade of water over the flying bridge, drenching Admiral Eberhardt and his staff. In return, the Russians landed one heavy caliber shell on Yavuzs forecastle, and another on her forward armoured belt. Outnumbered and outgunned, Captain Ackermann ordered his ship to disengage at 08:12. The Russians pursued the battlecruiser to the north before it doubled back and returned to Ottoman waters.