[5][Note 2] UB-10 was part of the initial allotment of seven submarines—numbered UB-9 to UB-15—ordered on 15 October from AG Weser of Bremen, just shy of two months after planning for the class began.

During this campaign, enemy vessels in the German-defined war zone (German: Kriegsgebiet), which encompassed all waters around the United Kingdom, were to be sunk.

[11] The UB I boats of the Flanders Flotilla were initially limited to patrols in the Hoofden, the southern portion of the North Sea between the United Kingdom and the Netherlands.

On 14 April, Steinbrinck and UB-10 sank their first ship, the 2,040-ton Dutch steamer Katwijk, 6 nautical miles (11 km; 6.9 mi) west of the North Hinder Lightship.

[16] The Belgian ship Menapier, carrying a load of iron ore from Algiers for Middlesbrough, was torpedoed and sunk off North Foreland by Steinbrinck on the 7th.

[20] Even though none of the boats sank any ships, by successfully completing their voyages, they helped further prove the feasibility of defeating the British countermeasures in the Straits of Dover.

[16][21] All eight of the sunken ships were smacks—sailing vessels traditionally rigged with red ochre sails[22]—which were stopped, boarded by crewmen from UB-10, and sunk with explosives.

[24] The same day, Fulgens, a 2,512-ton collier, was torpedoed one nautical mile (1.8 km) from Palling;[25] the crew of the ship—UB-10's largest victim to-date[16]—were all saved.

[16] The 4,243 GRT Rosalie, headed from North Shields for San Francisco, was torpedoed 3 nautical miles (5.6 km; 3.5 mi) from the Blankeney Buoy.

[32] On 18 August, the chief of the Admiralstab, Admiral Henning von Holtzendorff, issued orders suspending the first offensive.

The suspension was in response to American demands after German submarines had sunk the Cunard Line steamer Lusitania in May 1915, along with other high-profile sinkings in August and September.

Holtzendorff's directive ordered all U-boats out of the English Channel and the South-Western Approaches and required that all submarine activity in the North Sea be conducted strictly along prize regulations.

[35] The Huntly was the former German hospital ship Ophelia, which had been seized by English naval forces and renamed the previous year.

[40] UB-10's first victim in the new offensive (and Saltzwedel's first as a commander), came on 19 March when the U-boat torpedoed Port Dalhousie, a 1,744-ton Canadian steamer, 2 nautical miles (3.7 km; 2.3 mi) from the Kentish Knock Lightvessel.

[41] Nineteen men on the ship—headed from Middlesbrough to Nantes with a cargo of steel billets—were lost in the attack;[41] the mate, a pilot, and five crewmen were rescued.

[42] About two weeks later, UB-10 torpedoed and sank the Norwegian steamer Peter Hanre in nearly the same location; fourteen men on the 1,081-ton cargo ship were lost.

[45] In support of the operation, UB-10 and five other Flanders boats set out at midnight 30/31 May to form a line 18 nautical miles (33 km; 21 mi) east of Lowestoft.

[46][Note 4] This group was to intercept and attack the British light forces from Harwich, should they sortie north to join the battle.

[47] In mid-June, Saltzwedel was transferred to UC-10, and—as was the case with Steinbrinck—went on become one of the top-scoring U-boat commanders of the war, placing eleventh on the list with 150,000 tons to his credit.

[50] Since the early stages of the war, the Royal Navy had blockaded Germany, preventing neutral shipping from reaching German ports.

By the time of the so-called "turnip winter" of 1916–17, the blockade had severely limited imports of food and fuel into Germany.

[52] With the blockade having such dire consequences, Kaiser Wilhelm II personally approved a resumption of unrestricted submarine warfare to begin on 1 February 1917 to help force the British to make peace.

When encountered by UB-10, Amstelstromm was found "derelict and badly damaged" after shelling by German destroyers V44, G86, and G87; von Rohrscheidt launched a coup de grâce at the stricken ship and sent it down 20 nautical miles (37 km; 23 mi) east-northeast of the North Hinder Lightvessel.

[56] As UB-10 was returning to Zeebrugge in early April, she was attacked by a British submarine near the area where she had escaped from HMS E54 the previous August.

During other raids, considerable damage to harbour facilities delayed repairs and impaired the flotilla's ability to operate at full strength.

[3] After the Meuse-Argonne Offensive started on 26 September and the Allies began to drive back the German lines, plans were made to evacuate Flanders and dismantle the naval facilities at Bruges, Zeebrugge, and Ostend.

[3] All the vessels that were seaworthy were ordered to depart Flanders for Germany on 1 October; those unable to make the journey under their own power were to be destroyed.