On 10 June 1915, Heimburg, in command of sank the off
Porto di Piave Vecchia in the northern
Adriatic. On 6 July 1915, Heimburg, in command of with a crew of 14, torpedoed and sank the while operating under the Austrian flag off
Venice. On 16 July, Heimburg sailed for the
Dardanelles. This was at a time when the range of submarines was very limited. To reach
Bodrum,
UB-14 had to be towed a considerable part of the distance by an Austrian
destroyer. Even so, her engine broke down off
Crete and her compass became defective. Despite these problems, she arrived at Bodrum on 24 July. On arrival, she recharged the batteries of , which had arrived four days earlier with engine problems. A maintenance team then had to travel from
Constantinople to carry out necessary repairs to both submarines. At the time, this journey was not easy, being made partly by
train and partly by
camel. On 12 August, Heimburg sailed from Bodrum for the known steamer route between
Alexandria and the Dardanelles. His first sighting was of a fully lit hospital ship seen that evening which was not attacked. On 13 August, he first sighted the liner , in service as a hospital ship. He then sighted the , sailing unescorted for
Madras. He fired one
torpedo from under a mile away which hit her stern.
Royal Edward sank quickly in position six miles west of
Kandeliusa in the
Aegean Sea. The after deck was awash in three minutes, and the ship sank by the stern in six minutes. The death toll included 132 crewmembers and perhaps 1000 soldiers, though figures vary. The survivors were picked up by
Soudan, two French destroyers and some trawlers.
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. In August, Heimburg damaged the British
troopship Southland, bound for
Gallipoli. Approximately thirty men were killed, while the remaining troops and crew were rescued by nearby ships. A skeleton crew of volunteers managed to keep the ship afloat and beach it in
Moudros harbour. On 4 September, the British
submarine became entangled in enemy
torpedo nets off
Nagara Point in the
Dardanelles. All attempts to free the submarine failed. However, they had caught the attention of Heimburg, currently in harbour with
UB-14, which was undergoing repairs at nearby
Çanakkale. He visited the spot in a small
skiff, from which he lowered a small explosive charge.
E7 was forced to the surface. Her crew scuttled her before they were taken as
prisoners of war. On 5 November, Heimburg torpedoed and sank the British submarine . After taking command of , he also torpedoed and sank the on 19 June 1917. On 11 August, Heino von Heimburg was awarded the
Pour le Mérite. ==Interwar period==