U 73, chronological list of events from January 1915 until September 1917
(All dates are in accordance with the new Revised Julian Calendar).
- At the request of the German Imperial Navy (Deutsche Kaiserliche Marine) the construction of a new Class UE 1 submarine, designated as U-73 commences at the Imperial Kaiserliche Werft shipyards, west of Danzig, Prussia (now Poland).
- Launching of U-73.
- After her delivery, the U-73 is put into service under the command of Kapitänleutnant Gustav Siess.
- The mission of this U-boat is to set mines in areas where passages of ships of the Entente are frequent.
14. – 25.02.1916
- Exercises and testing of the u-boat in the North Sea.
- During the exercises, on 16.02.1915, a large wave swept the deck, taking with it the duty officer, Lt. Commander (Oberleutnant zur See) Wolff. The rescue efforts remain fruitless as weather conditions do not allow for a search and rescue operation of the unfortunate navy officer.
- The U-73, under the orders of the commander of Kapitänleutnant Gustav Siess, departs from Kiel (Germany) heading to the Mediterranean Sea.
- The U-73 joins the German submarine fleet of the Mediterranean (Deutsche U-Flotille Pola), which uses the bases of Pola Istria (now Pula, Croatia) and Cattaro of Dalmatia (now Kotor, Montenegro). Areas which were at the time belonging to the Empire of Austria-Hungary.
- The U-73 is at Helgoland, the only oceanic island of Germany.
- The Helgoland during both world wars, was an important naval base for the German Navy.
- The U-73 is at the northern edge of the Shetland islands. A cluster of islands between Scotland and Norway.
- U-73 sinks by use of her gun the British sailing ship Inverlyon, of 1.827 GRT displacement, at the southern tip of Ireland.
- During the sinking of Inverlyon, a large wave swept from the submarine’s deck the sailor Pehrson. Large waves and bad weather hamper the search and rescue operation.
- Early in the morning, positions 12 mines, in two groups at the entrance of the port of Lisbon (Portugal). Designated as Minefield No. 15.
- On the same day the Norwegian ship Terje Viken, of 3.580 GRT displacement sinks after hitting a mine of this minefield.
- The U-73 passes the Straits of Gibraltar and enters into the Mediterranean Sea.
- At dawn positions 22 mines at the entrance of the port of La Valetta in Malta. Designated as Minefield No. 17., On the same day the the British ship HMS Russel, of 14.200 GRT displacement and the British K-107 corvette HMS Nasturtium, of 1.250 GRT displacement hit this minefield and sink.
- On 28.04.1916 sinks after collision in the same minefield, the British Yacht Aegusa, of 1.242 GRT displacement.
- The U-73 reaches the naval base of Cattaro (former Austro-Hungary, now Montenegro).
24.07. – 14.08.1916
- Operates in the Aegean Sea.
- The U-73 positions mines in the Gulf of Thessaloniki. Designated as Minefield No. 19.
- Positions more mines in the Gulf of Orfanou (Strymonikos bay). Designated as Minefield No. 20.
- At dawn of the same day sinks by torpedo the British minesweeper Clacton, of 820 GRT displacement.
- Places mines in the western entrance to the Gulf of Moudros in Lemnos island. Designated as Minefield No. 21.
- Sinks in the Ionian Sea, during her return to the Cattaro base, the Italian sailing Lorenzo Donato, of 140 GRT displacement.
22.10. – 07.11.1916
- Operates in the Aegean Sea.
- Conduct of Commerce Raids (Handelskrieg in German, Guerre de Course in French).
- Sinks with explosives, in the Ionian Sea, the Greek sailing vessel Propontis, of 700 GRT displacement, which was loaded with cement and heading from France to Port Said, Egypt.
- The U-73 lays minefields in two places east and west of Fleves island in the Saronic Gulf. Designated as Minefield Number 31.
- Positions 12 mines in the Kea Channel. Designated as Minefield Number 32.
- On 14.11.1916, the S/S Burdigala, of 12.380 GRT displacement, heading from Salonika towards Toulouse, sinks, probably from a mine, exactly at the point where 18 days before the U-73 had laid the Minefield Number 32.
- Historical sources mention two versions regarding the sinking of the S/S Burdigala; the French states as cause a torpedo hit (see Auguste-Antoine Thomazi, p. 180), and the British reports a mine hit (see Paul G. Halpern, p. 253). The German sources (see Arno Spindler, 3rd Volume, p. 343), considers as the cause of sinking of the ship from a mine hit, but the Greek press of the time (see newspaper “Empros” on 2 and 3 November 1916, Gregorian Calendar) adopts the French version, and reports that the ship «Vordygála» was sank in the Kea Channel by a German torpedo.
- Exactly one week later (21.11.1916) in the same area, the British hospital ship HMHS Britannic sinks from a mine hit, the largest ocean liner of the time (and sister ship of the Titanic) with a displacement of 48.158 GRT.
- Places another 12 mines between Tinos and Mykonos. Designated as Minefield Number 33.
- At this point, on 23.11.1916, the hospital ship HMHS Braemar Castle is grounded, after a hit from a mine laid by the U-73.
31.10. and 04.11.1916
- The U-73 fires a torpedo on 31.10 and then again on 04.11.1916, against two cargo ships but without success.
- All her munitions of torpedoes and mines are depleted. Because the Commerce Raids (Guerre de course) to be carried out on the surface was not possible, due to the continued presence of Entente destroyers, the U-73 heads for its Cattaro Naval Base.
- The U-73 drops anchor at the Cattaro Naval Base and remains there awaiting repair of her engine oil pumps.
10. – 30.12.1916
- Positions 22 mines in four groups outside of Port Said. Designated as Minefield number 41.
- During the voyage from Port Said to Alexandria, the U-73 sinks by torpedo the British tanker Murex, of 3.564 GRT displacement.
- The U-73 positions 12 mines outside the port of Alexandria. Designated as Minefield number 42.
- Sinks the British armed cargo vessel Thistleban, of 4.117 GRT displacement, after hitting a mine from the number 42 minefield.
- During her return to base, the U-73 is unable to attack a sail ship because of mechanical failure.
- After her return to the Cattaro Naval Base, the submarine remains idle for a long period due to mechanical repairs until September 1917.