Transformer un paquebot en arme de guerre ?

Liners can be repurposed during wartime by replacing passengers with soldiers, goods with ammunition and supplies, or even being converted into floating hospitals and armed warships.

The First World War erupted during the golden age of large liners, a period when ships were increasingly bigger and faster, making them valuable military assets.

The concept of using liners for military purposes began in the 1860s when Napoleon III granted the General Company transatlantic postal contracts with military use in mind, particularly for operations in Mexico.

By the eve of the First World War, the possibilities for converting liners into military vessels were extensive and well-established.

The British military navy was expensive to maintain during peacetime, while merchant ocean liners were growing bigger and faster, presenting an opportunity to fulfill escort and patrol roles while maintaining commercial service.

• The Teutonic, launched by White Star Line in 1889, was funded mostly by the Admiralty • Followed by its twin ship Majestic, both designed as auxiliary cruisers • Ships received military subsidies in exchange for meeting military security standards and easy transformation capability

The Teutonic impressed German Kaiser William II during inspection at Spithead, leading Germany to commission similar vessels like the Kaiser Wilhelm der Grosse and others for future war service.

The British Admiralty signed contracts with Cunard Line for the Mauretania and Lusitania, the fastest and tallest liners of the time, which could also serve as auxiliary cruisers. The Mauretania maintained the speed record until 1929, and Aquitania joined them before World War I.

When war erupted in August 1914, the primary role of ocean liners shifted to evacuating American tourists caught by surprise in the conflict back to safety before conditions deteriorated.

• Passengers learned of war while crossing the Atlantic and feared becoming prisoners • Surreal scenes occurred in lounges as passengers from opposing nations embraced each other • In some ports, Americans lined up for hours to book passages, willing to travel overcrowded

Liners operated with all lights off to avoid detection, crews avoided radio contact, and ships were painted gray for reduced visibility during these dangerous crossings.

• German liners like Vaterland, then the world's largest, took refuge in neutral American ports • The German liner Kronprinzessin Cecilie painted its yellow chimneys black to resemble the British Olympic while carrying gold to America • Both sides worked to ensure their most valuable vessels reached safe harbors

• Several premier British ships were requisitioned as soon as they arrived at port • Luxurious decorations were removed and stored; cannons were installed • A Navy captain complemented the civilian captain to maintain military control • Ships joined cruiser squadrons or escorted troop convoys from British Dominions, especially Canada

The Oceanic, a British liner in military service, was lost during patrol operations when confusion between the two captains caused it to veer off course and hit rocks before sinking.

The German liners Kaiser Wilhelm der Grosse and Kronprinz Wilhelm were armed to attack merchant ships in the Atlantic, boarding them for valuable cargo, allowing crews to escape, and then scuttling the ships.

• Kaiser Wilhelm der Grosse sank on August 26, 1914, after taking three ships and stopping to restock • Kronprinz Wilhelm attacked around fifteen ships until spring 1915 when epidemic and coal shortage forced refuge in an American port • The Kronprinz Wilhelm's crew famously thanked their enemies in the American press for poorly protecting ships they could raid for supplies

Submarines quickly became a far more formidable danger than surface raiders. Initially seen as coffins floating, by late 1914 their torpedoes inflicted heavy damage on the British fleet, alongside mines that sank many vessels.

• The Lusitania was the only large ocean liner to continue commercial service in 1915, hosting elite clientele • On May 7, 1915, it was torpedoed off the Irish coast by a German submarine • The ship sank taking many civilians, including several American citizens, shocking neutral American opinion

In August 1915, the White Star's Arabic was torpedoed in the same area where Germans had promised to cease attacking civilian ships without warning. Three Americans perished, again shaking American public opinion.

Germany temporarily reduced submarine warfare to preserve American neutrality, but resumed excessive submarine warfare in 1917, which ultimately helped bring the United States into the conflict.

• The Olympic transported soldiers across the Mediterranean to operations in Turkey, including the bloody Dardanelles campaign • The France, a luxury liner from 1912, was transformed to transport about 4,000 soldiers to the Dardanelles • Conditions were terrible with Ottoman artillery, German aircraft, and constant rotation of wounded soldiers

Large ocean liners quickly became hospital ships, with France, Mauretania, Aquitania, and Britannic serving in this capacity. The Britannic was the twin of the Titanic and had never served commercially.

• In November 1916, during its sixth voyage, the Britannic was shaken by a violent explosion off the Greek island of Kea • The explosion, likely from a mine, occurred during extremely hot weather when portholes were left open for ventilation • Open portholes and watertight doors allowed water to rush in, causing the ship to sink in less than an hour

• Fortunately, no one aboard was killed; only about thirty victims resulted from those who left in lifeboats without orders and were caught in the ship's propellers • Propaganda suggested the Britannic was attacked as a war crime, but the mine thesis is now accepted as most likely • The sinking demonstrated the dangers faced by hospital ships during the conflict

With American entry into the war, the golden hour arrived for liners and freighters as they needed to transport all American troops to Europe and supply them with materials, food, and oil.

• From 1917, the entire fleet of ocean liners went under British military control • In 1918, French liners were requisitioned by the State, causing concern among companies about compensation in case of defeat • Americans seized German liners that had taken refuge in neutral American ports

• The Vaterland became the Leviathan under the American flag, serving as an ocean liner into the late 1930s • German companies lost their fleets during the war • Largest German liners were sold to British and French companies as war reparations

• Atlantic crossings were tough for troops and crews, with dangers extending until 1919 • The Olympic was attacked by a submarine in 1918 but responded by going at full speed, sinking the submarine • Torpedo impacts on the Olympic's hull went unnoticed, with no explosions, evidence of narrow escapes

• Dazzle camouflage was invented by painter Norman Wilkinson • Geometric shapes painted in irregular patterns and colors made ships harder to distinguish, especially during zigzag maneuvers • It didn't make ships less visible but made their trajectory difficult to calculate, preventing accurate torpedo targeting • The result was distinctive 'war uniforms' for vessels

Many liners were sunk from British and French fleets during the war, while the largest German liners often remained hidden in ports.

• Military contracts, profits, and compensations benefited winning companies • The General Company transatlantic's profits exploded from 1914 • Companies profited from war but also faced extreme risk; if France lost, major losses would follow

• German shipping companies had their fleets stripped after the war • The Imperator and Bismarck were sold to Cunard and White Star, becoming Berengaria and Majestic • HAPAG, the world's largest shipping company, fell apart; its president Albert Ballin committed suicide on November 9, 1918, two days before the armistice

The First World War experience with liners was not unique; these ships played an even larger role during World War II.

• World War II saw the two deadliest shipwrecks in history in 1945 • Cap Arcona with 5,000 dead, mostly prisoners from camps • Wilhelm Gustloff with 10,000 refugees who disappeared

• Troop transport operated on an even larger scale than in World War I • Photos showed overloaded bridges of Queen Mary and Queen Elizabeth • Italy to Japan, liners were sometimes transformed into aircraft carriers with varying success

From luxury liners to hospitals, cruisers, pirates, and aircraft carriers, these ships symbolized how total war transformed everything in society, pushing everything far away from what a world at peace looked like.