The ship continued to operate with the fleet through 1915, in addition to her U-boat flagship duties. While cruising off the mouth of the Weser river on 21 April, she accidentally collided with the torpedo boat , breaking her in half and sinking her. "Hamburg" had to be drydocked for repairs, though these were completed in time for the ship to participate in a fleet sortie on 17–18 May. Another operation followed on 29–30 May; the ship saw little activity until the fleet conducted another sweep into the North Sea on 11–12 September, by which time the "II. Führer der Torpedoboote" (2nd Commander of Torpedo Boats), "Kommodore" (Commodore) Karl von Restorff had hoisted his flag aboard "Hamburg". A final operation for 1915 took place on 23–24 October. None of the year's operations had resulted in contact with elements of the British Royal Navy. The fleet continued these operations in 1916, with sorties on 5–7 and 25–26 March and 21–22 and 24–25 April, the last of which resulted in the raid on Yarmouth and Lowestoft.