On 10 June 1915, Heimburg, in command of UB-15 sank the Italian submarine Medusa off Porto di Piave Vecchia in the northern Adriatic.

[1] On 6 July 1915, Heimburg, in command of UB-14 with a crew of 14, torpedoed and sank the Amalfi while operating under the Austrian flag off Venice.

Royal Edward sank quickly in position 36°13′N 25°51′E / 36.217°N 25.850°E / 36.217; 25.850 six miles west of Kandeliusa in the Aegean Sea.

UB-14 did not harass the rescue effort, but headed back to Bodrum with some technical problems, arriving on the morning of the 15 August.

Approximately thirty men were killed, while the remaining troops and crew were rescued by nearby ships.

On 4 September, the British submarine E7 became entangled in enemy torpedo nets off Nagara Point in the Dardanelles.

While interviewing German veterans of the U-boats, American journalist Lowell Thomas was introduced to Heimburg by Lothar von Arnauld de la Perière.