"U-30" went to sea on 22 August 1939, before World War II began. Her active service career began on 3 September 1939, just 12 days after leaving Wilhelmshaven and only 10 hours after Great Britain declared war on Germany, she sank the 13,581-ton passenger ship SS "Athenia" about west of the Hebrides while she was en route from Liverpool to Montreal in Canada. The "Athenia" was the first ship sunk in World War II; out of 1,400 passengers, 112 of them, including 28 neutral Americans, died. After sinking "Athenia", "U-30" went on to sink two more vessels, "Blairlogie" and the .