New Zealand's overwhelming dependence on sea trade and close economic ties to Britain ensured that merchant ships and seafarers played an essential role in the First World War. The name Merchant Navy, which hints at this civilian industry's wartime importance, was adopted in Britain in the early 1920s. It recognised the effort and sacrifice of the British Empire's merchant marine – as it was then better known – during the Great War, when 2500 ships and 15,000 seafarers were lost.
Many New Zealanders served on the British-owned 'Home boats' that linked this country with the United Kingdom. Others worked for Dunedin's Union Steam Ship Company, then the Southern Hemisphere's biggest shipping line. The Union Company's large, modern fleet was one of this country's most valuable war assets: its vessels served as troop transports, hospital ships and in many other roles. Although they were civilians, many New Zealand merchant seafarers found themselves in the firing line, especially in the far-off North Atlantic, where the German U-boat menace threatened to turn the tide of the war.