After almost a month undergoing normal repairs the SMS UC-77 departed Zeebrugge, Belgium on July 11, 1918 for another war patrol. This had been a successful boat for the Kaiser, sinking 34 ships for over 50,000 tons during her career, which began when she was commissioned on Dec. 29, 1916. The first victim of the boat was the 1,438 ton Norwegian freighter Grenmar on Mar. 24, 1917, her last direct victim was the 1,303 ton British freighter Moidart, torpedoed on June 9, 1918, however a mine laid by UC-77 is credited with sinking the British trawler Princess Olga on June 14.

Her commanding officer for this patrol was Oberleutnant zur See Johannes Ries, he had been in command of the boat since Jan. 30, 1918, but had commanded two other U-boats before, UB-17 and UB-88. UC-77 was his last command, for after leaving port, the boat was never heard from again. To this day what happened to her and the thirty-one men in her is still unknown. The best guess is that she was mined, but of course this is always the best guess, however there is a range of other causes which can not be ruled out since the wreck has not been located to my knowledge. An unidentified wreck off the coast of Flanders may be that of the lost boat, but this has not yet been confirmed.

Ironically the first boat that Ries commanded met the same fate, four months to the day earlier, UB-17 sailed from Zeebrugge on Mar. 11, 1918 and was never heard of again. The wreck of this boat is also still missing.