U-27 was built by the Austrian firm of Cantiere Navale Triestino (CNT) at the Pola Navy Yard and launched on 19 October 1916.

[2][Note 2] After these steps alleviated their most urgent needs,[4] the Austro-Hungarian Navy selected the German Type UB II design for its newest submarines in mid 1915.

[2] After intricate political negotiations to allocate production of the class between Austrian and Hungarian firms,[6] U-27 was ordered from Cantiere Navale Triestino (CNT) on 12 October 1915.

[2][6] After her completion, U-27 was commissioned into the Austro-Hungarian Navy on 24 February 1917 under the command of Linienschiffsleutnant Robert Teufl von Fernland.

About 5 nautical miles (9.3 km; 5.8 mi) off Augusta, Sicily,[10] U-27 shelled and sank the 11-year-old Greek ship.

Carrying coal from Barry for Taranto, Zinovia was sent to the bottom 5 nautical miles (9.3 km) from Cape Rizzuto.

On the night of 14/15 May, the Austro-Hungarian cruisers Helgoland, Saida, and Novara attacked the drifters that deployed the anti-submarine nets that formed part of the Barrage, sinking 14, damaging 5, and taking 72 prisoners.

As a result of the attacks the drifter line of the Barrage was moved farther south and maintained only during the day, a success for the Central Powers.

[16] Although the Japanese ships often performed escort service for British troop convoys,[16] Helgason does not report whether Sakaki was engaged in that duty when she was attacked.

[22][23] Phoenix had been attached to the group of ships patrolling the Otranto Barrage when she was torpedoed amidships on the starboard side.

[24] Although she survived the initial attack, Phoenix was listing badly and taking on large quantities of water.

An attempt was made by Australian destroyer Warrego to tow Phoenix to safety but by 12:45 she was in danger of capsizing and her crew were removed.

[25] From 3 to 11 July, U-27 sank another nine ships,[21] the largest reported being the 53 GRT sailing vessel Tris Adelphi.

[28] Starting three days later, Holub and U-27 sent an additional twelve small ships to the bottom, including the final six all on 20 September.