The London North Western Railway Company (LNWR) maintained their Holyhead to Dublin express service by switching the two Greenore ships to the Dublin service. An older ship was on standby.
The potential of U-boats to destroy shipping had hardly been understood before the war and Britain and Germany quickly discovered what even a handful of them could do. A U-boat was nearly impossible to detect when submerged, so it could slip unnoticed through the Dover straits or around Scotland. Diesel engines gave German submarines a range of several thousand miles. They could wait submerged and unseen for several hours before launching attacks, such as that which sank the Lusitania off the coast of County Cork. They could sink ships by gunfire or torpedo, and lay mines. Once decoy ships, also known as Q-ships, were used to ambush U-boats, the German naval command responded by sinking targets on sight and without warning. At the same time, Germany built more and more submarines.
The British Admiralty response was to create the Auxiliary Patrol which consisted of hundreds of trawlers and drifters based in ports around the country including Queenstown (now Cobh), Kingstown (now Dún Laoghaire), Holyhead and Milford Haven. They faced a steep learning curve on how to combat the U-boat threat. Minesweeping became effective. Technical advances like guns, wireless, and effective mines and depth charges helped. Much time was spent on patrolling, hunting for submarines, but whether it was effective has been disputed. What was needed was a way of detecting submarines underwater, which only happened late in the war.
With the German move to a second wave of unrestricted submarine warfare in February 1917, Queenstown developed into one of the main bases of the escort forces for ocean convoys. US destroyers started to arrive in May and by late summer the inward and outgoing convoying systems were working successfully.
The German switch to attacking coastal shipping in autumn 1917 caused significant losses and casualties to unescorted Irish owned shipping in the Irish Sea that lasted into 1918. Following the loss of three Dublin based ships, SS Hare, SS Adela and SS Cork, in December 1917 and January 1918, Irish MPs pressed for a commitment to escorts in the House of Commons.
The City of Dublin Steam Packet Company (CoDSPCo) owned SS Cork, was torpedoed and sunk off Anglesey at the end of January with the loss of twelve passengers and crew. One passenger casualty, 22-year-old Elizabeth Garvey had lived with her widowed mother Bridget in a tenement room near Mountjoy Square.
The inhabitants of this poor area in Dublin included Sean O’Casey and they were the raw material for his plays. He was interested in the relationships between mothers and their children and he may have absorbed the story of Elizabeth’s death. And used it.
The introduction of unrestricted submarine warfare and subsequent convoying meant the end of the Q-ship as a useful weapon. Ships sailing alone, as Q-ships did, were suspect, and if they were spotted then the U-boat did not approach them, but stood off and sank them by gunfire or torpedo. On 11 February 1918, the Q-ship HMS Cullist (formerly SS Westphalia) was on patrol off Drogheda when she was torpedoed and sunk by U 97. Around 45 of her crew of 70 were killed.