Before 1914 many great ocean liners sailed as emigration to the United States increased. At a time when there were no passenger planes, ocean liners provided the only pathway to cross the oceans. Once war in Europe had begun, many of the great ocean liners of the period withdrew from transatlantic crossings. However, they still remained at sea.

Some liners did maintain their regular voyages in 1914 and 1915. One of the more notable was the Lusitania that transported thousands more during the early war period. But whilst they still remained civilian ships, they could still transport armaments and munitions back to the United Kingdom.

The Lusitania was loaded with a small amount of munitions cargo on its final voyage to the U.K. in 1915. One German U – boat intercepted the liner off the south coast of Ireland and fired a torpedo. This torpedo had enough impact to sink the Lusitania within a period of 30 minutes which gave little time for the thousands aboard to abandon ship.

The loss of the Lusitania was not the last time a liner was lost during this war. The Britannic was another that sailed during the period. However, unlike the Lusitania the Admiralty had requisitioned this ship to transport troops to and from the Mediterranean. The size and scale of ocean liners such as the Britannic and Olympic made them ideal for transporting larger number of troops.

With the Gallipoli Campaign expanding in 1915, the Mediterranean was the primary destination for the Britannic. In November 1916, the ship sailed for the Greek Island of Lemnos. Before it reached the destination, an explosion triggered by an underwater mine ensured the flooding of the Britannic off the coast of Kea. Fortunately a variety of naval units remained within the ship's proximity to pick up those in the water after it had gone down.

The BritannicCredit: Public Domain

The other Olympic-class ocean liner of the period was the Olympic, and this was converted to a troop transport ship. Armaments and black and white dazzle paint were added to the former ocean liner to give it additional camouflage from German U – boats. During the period it transported many thousands of troops to various destinations up to 1918.

In 1918, the Olympic spotted a German U – boat that had surfaced a few hundred meters ahead of it. After spotting the submarine, the Olympic turned and rammed it, which had enough impact to ensure that the crew scuttled and abandoned the U – boat. For the first time in that war a merchant vessel had taken out a warship.

Other ocean liners were not merely troop transport and supply ships during the period. Germany converted liners to auxiliary cruisers, with additional cannons added to them. One of the more notable former ocean liners converted to an auxiliary cruiser was the Kaiser Wilhelm Der Grosse. This was the first German ocean liner to set Blue Riband records, and could reach up to 22.5 knots on the high seas.

In 1914, the Kaiser Wilhelm Der Grosse became a cruiser, and was suitably camouflaged. Then it wiped out a couple of freighters in 1914. Later that year a British cruiser discovered it refueling at Río de Oro off the west coast of Africa. In the naval skirmish that followed the Wilhelm Der Grosse ran out of ammunition, so the orders were given to scuttle the ship.

Another of Germany's liners was the SS Kronprinz Wilhelm. In much the same way as the Kaiser Wilhelm Der Grosse, the Imperial German Navy converted it to an auxiliary cruiser. From 1914 – 1915 the German navy sent it on various commerce raiding missions in which it captured 14 British and French merchant vessels at sea.

When the ship ran out of supplies in 1915, it remained in a U.S. port until the United States declared war with the German Empire. The Americans repaired it and added it to the U.S. Navy in 1917. Then it transported U.S. troops up until 1918.

These were just a few of the great ocean liners that sailed during that war.[1] As troop and supply ships they transported thousands of reinforcements to various fronts. In a combat role Germany's former liners were more effective as auxiliary cruisers, which took out and captured a number of Entente merchant ships. After the 1918 armistice those that remained at sea, such as the Olympic, sailed as ocean liners once more.