The particular mission when Gulflight was attacked commenced 24 April 1915. On 28 AprilU-30 intercepted the collier Mobile which she sank by gunfire after allowing the crew to escape. On 29 April she similarly sank the 3,200 GRT Cherbourg. 30 April she ordered the steamer Fulgent to halt, but when the ship failed to do so fired a shot into the ship's bridge, which killed the captain and quartermaster. The ship stopped and the rest of the crew were allowed to escape before the ship was sunk by explosive charges placed inside. That afternoon, the 3,100 GRT Svorno was stopped and sunk. On 1 May the grain carrier Edale and French ship Europe were sunk. A Dutch ship was stopped and, as a neutral, permitted to continue at a point some north west of the Scilly Isles, but the submarine was spotted at this point by a steam drifter, Clara Alice which reported her position to a naval patrol. The patrol ships and started to hunt for the submarine, but succeeded only in intercepting the US-flagged Gulflight, which they took under escort. The escort proved something of a disadvantage to Gulflight because she was obliged to slow down for the patrol and then, under international law, as a ship escorted by armed vessels became a legitimate target for attack. U-30 spotted the convoy and fired one torpedo at Gulflight, before noticing that she was flying an American flag. The submarine then broke off the attack in accordance with her instructions not to attack neutral vessels. Gulflight survived the attack, although two members of the crew drowned while evacuating the ship and the master Captain Gunter died later that night from a heart attack. The ship was towed to Crow Bay and later repaired. News of the event would be overshadowed a few days later by the sinking of but the incident, together with the attack on Lusitania and another ship, Cushing, formed the basis of a formal complaint from the US government to Germany. Although the United States remained officially neutral in the ongoing hostilities, it reached agreement with the German government that further attacks by submarine would be strictly in accordance with "cruiser Rules" as defined by international law.
