First journey

Deutschland departed on her first voyage to the US on 23 June 1916 commanded by Paul König, formerly of the North German Lloyd company. On her maiden voyage, she carried 750 tons of cargo in total, including 125 tons of highly sought-after chemical dyes, mainly Anthraquinone and Alizarine derivatives in highly concentrated form,^[4] some of which were worth as much as $1,254 a pound in 2005 money. She also carried medical drugs, mainly Salvarsan, gemstones, and diplomatic mails, her cargo being worth $1.5 million in total ($42 million in 2024).^[5]

Deutschland waited a week at Heligoland after the announced sailing date to avoid enemy patrols. She submerged for only 90 miles (140 km) of the 3,800-mile (6,100 km) outbound voyage.^[6] Deutschland did not enter the English channel but took a northern passage around Scotland.^[7] At about 600 nmi (690 mi; 1,100 km) off the Virginia capes lookouts sighted a possible hostile ship so that Deutschland submerged, altered course back to sea and then approached submerged until about 100 nmi (120 mi; 190 km) of the Chesapeake Bay entrance. At 1:20 a.m. on 9 July Cape Henry was sighted and contact made with the Eastern Forwarding Company tug Thomas Timmins which had been specially altered to tow Deutschland alongside and been waiting some days.^{[Note 1]} At 11:00 p.m. on 9 July 1916 the two vessels reached Baltimore.^[8] She arrived at the Quarantine anchorage off of Marley Neck, Anne Arundel county, just outside of what was then Baltimore city limits.^[7] after just over two weeks at sea. A photograph by Karle Netzer was made the next morning, 10 July. (erreichte Baltimore Hafen 10 Juli 1916).^[9] During their stay in Baltimore, the German crewmen were welcomed as celebrities for their astonishing journey and even taken to fancy dinners and an impromptu volksfest in the southwest part of the city. American submarine pioneer Simon Lake visited Deutschland while she was in Baltimore, and made an agreement with representatives of the North German Lloyd line to build cargo submarines in the US, a project which never came to fruition when the United States declared war on Germany in early April, 1917.^[10]

She stayed at Baltimore until 2 August, when she sailed for Bremerhaven, arriving on 24 August with a cargo of 341 tons of nickel, 93 tons of tin, and 348 tons of crude rubber (257 tons of which were carried outside the pressure hull). Her cargo was valued at $17.5 million, several times the submarine's construction costs.^[10] She had traveled 8,450 nmi (15,650 km; 9,720 mi), having been submerged for 190 nmi (350 km; 220 mi) of them.

The successful completion of this first voyage was commemorated with a tongue-in-cheek medal created by German artist Ernst Zehle, with a dedication to the British Lord Robert Cecil, responsible for the blockade, on the front. On the reverse is a beaver swimming under some fishermen's nets with the phrase "Don't go over! Go under!"

Second journey

Deutschland made a second round trip in November 1916. This time she went to New London, Connecticut, where the Norddeutscher Lloyd ship Willehad was waiting as her submarine tender. Deutschland discharged $10 million of cargo ($ 280,000,000 in 2024) including gems, securities, and medicinal products. At the same time the submarine U-53 also crossed the Atlantic to visit Newport, Rhode Island, and sank five Allied cargo ships just outside US territorial limits before returning home.

On 17 November as she was putting to sea, Deutschland accidentally rammed the tugboat T. A. Scott, Jr., which turned across her path suddenly while escorting her from New London to the open ocean. T. A. Scott, Jr., sank immediately with the loss of her entire crew of five. Deutschland's bow was damaged, and she had to return to New London for repairs, which delayed her departure by a week.^[12][13] She finally left New London on 21 November 1916, with a cargo that included 6.5 tons of silver bullion.

Following his last voyage, Captain Paul König collaborated to write a book about the journeys of Deutschland, entitled Voyage of the Deutschland, the First Merchant Submarine (Verlag Ullstein & Co, Berlin 1916, and, Hearst International Library Co., New York 1916). The book was heavily publicized, as it was intended to sway public opinion in both Germany and the US.^[14]

1917

During the summer of 1917 U-155 made a 105-day cruise, commanded by Kptlt. Karl Meusel, leaving Germany around 24 May and returning on 4 September. During her traverse of the Northern Passage around the northern end of the British Isles and out into the Atlantic Ocean, she was stalked and nearly sunk by U-19 near Utsira Island, Norway.

During this patrol, the boat fired on the port city of Ponta Delgada in the Azore Islands on 4 July at 3 a.m. with its deck guns. Portuguese army units did not respond due to being equipped with obsolete artillery. The collier USS Orion happened to be in port at the time undergoing repairs. Its company returned U-155's fire and dueled with the German boat for about 12 minutes. U-155 submerged without being hit and eventually retired. While the raid was light in damage (it killed four people), it alarmed Allied naval authorities about the defenseless nature of the Azores and their possible use as a base by boats like U-155 in the future. Allied naval forces, led by the U.S. Navy, began to send ships and establish a naval operating base in Ponta Delgada as a result.

During her patrol she sank 19 merchant ships, most by either scuttling or gunfire. She attacked 19 Allied armed merchantmen but only succeeded in sinking 9 of them. Upon her return to Germany she had covered a distance of 10,220 nmi (18,930 km; 11,760 mi), of which 620 nmi (1,150 km; 710 mi) had been travelled submerged, one of the longest voyages made by a U-boat during World War I.^[16]

1918

U-155 sailed from Kiel on 11 August 1918 commanded by Ferdinand Studt. Studt's orders directed him to cruise off the US coast in the region of the Nantucket lightship and lay mines off St. John's, Newfoundland and Halifax, Nova Scotia. He was also directed to cut telegraph cables off Sable Island, 80 km (50 mi) southeast of Nova Scotia. His orders, however, proved problematic, and Studt came to believe that the St. Johns where he was to lay mines was actually Saint John, New Brunswick, in the Bay of Fundy.

On U-155's outbound voyage she had captured and scuttled the Portuguese sailing ship Gamo, had attempted an attack on SS France, and destroyed by gunfire the Norwegian Stortind. On 7 September U-155 found herself in a long range gun duel with the US steamer Frank H. Buck, with the steamer later claiming to have sunk U-155.

On 13 September U-155 engaged in another gun fight with the British merchantman Newby Hall, which managed to damage the submarine, denting her armour and causing serious leaks in her pressure hull which made diving temporarily impossible.

On 19 September, Studt tried and failed to locate and cut the telegraph cable near Sable Island, then headed for Nantucket.^[17]