Known as the “Greyhounds of the Seas,” Lusitania and its sister ship, Mauretania, were the fastest passenger liners of their age, capable of crossing the Atlantic Ocean in under five days. At more than 30,000 gross tons each, they were also the world’s largest liners from their launch in 1906 until being surpassed by Olympic and Titanic in 1910 and 1911, respectively. Said to be “more beautiful than Solomon’s Temple and big enough to hold all his wives,” Lusitania attracted a plethora of wealthy, prominent passengers. On its ill-fated final voyage, for example, those onboard included millionaire heir Alfred Vanderbilt, Broadway producer Charles Frohman and actress Rita Jolivet, as well as art collector Hugh Lane, who was purportedly traveling with Rembrandt and Monet paintings stashed away in sealed lead tubes. They were joined by a former British member of Parliament, an amateur boxing champion and a special envoy to the king and queen of Belgium, not to mention businessmen, nurses, would-be soldiers and children. What’s more, as secret documents and evidence gathered at the wreck site would later show, Lusitania had 4.2 million rounds of rifle ammunition, 1,250 cases of shrapnel shells and 18 cases of non-explosive fuses hidden away in its cargo hold, bound for the Western Front.

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In February 1915, in an attempt to stop just such war material shipments—and to counter a crushing Royal Navy blockade—Germany adopted a policy of unrestricted submarine warfare in the waters around the United Kingdom. Even neutral ships, it declared, would be fair game. Though submarine technology had progressed by leaps and bounds in recent years, the effort got off to a slow start, with only seven vessels going down in the first two weeks. Persistence paid off, though, when amid other successes the Germans torpedoed the British passenger-cargo ship SS Falaba on March 28 at a cost of over 100 lives, including the first American casualty of World War I. Germany also engaged in some psychological warfare. On May 1, the same day as Lusitania’s scheduled departure from New York to Liverpool, the German embassy in the United States took out a warning in several newspapers reminding travelers that they went to Britain at their own risk. In some of those newspapers, the warning even appeared adjacent to a Lusitania advertisement. Yet almost no one canceled their trip. “It’s the best joke I’ve heard in many days,” said Lusitania’s captain, William Turner, whereas the Daily Telegraph in London called it “Berlin’s latest bluff.”

A little past noon on May 1, Lusitania gave three blasts of its horn as it left Pier 54 in New York City and began moving down the Hudson River to the Atlantic Ocean. With the weather cooperating, the first few days of the voyage proceeded uneventfully. Passengers whiled away the time reading, playing cards, listening to the ship’s orchestra and, in the spirit of any good cruise, eating copious amounts of food. A palpable tension settled over them, however, once Lusitania crossed into the war zone on May 6. They had good reason to be worried. The German submarine U-20 had made its way that week to the waters off the southern coast of Ireland, then part of the United Kingdom, and had already sunk a schooner and two steamers. Thanks to these attacks, along with intercepted wireless messages, the British Admiralty knew of U-20’s general location (and of other U-boats operating nearby). Nonetheless, it never sent a promised military escort to Lusitania, nor did it offer anything but general warnings about active submarines in the area.

Servicemen attend a mass funeral in Cobh, County Cork, Ireland for victims of the Lusitania disaster. (Credit: Topical Press Agency/Getty Images)

Although one of its four boiler rooms had been shut down to save coal, Lusitania could still easily outrun any German submarine when operating at full speed. But on the morning of May 7, fog and a desire to catch high tide at the shallow channel into Liverpool caused Captain Turner to slow down a few knots. Meanwhile, instead of zigzagging, which made it harder for submarines to aim, he charted a straight course that brought him right into the path of U-20. At 2:10 p.m., lookouts aboard Lusitania noticed a torpedo streaking toward them. By that time, however, it was too late to act. Detonating as it hit the starboard hull, the torpedo made the ship shake life a leaf, one passenger recalled. Then, just seconds later, a second explosion erupted from deep within the vessel, sending it careening to one side. To this day, the source of the second explosion remains a mystery. Some historians believe it was a boiler room blast, while others blame coal dust, a steam line rupture or the contraband munitions onboard.

With the engines and electricity knocked out and passengers racing to find both their life jackets and their families, chaos set in. One survivor said it reminded her of “a swarm of bees who do not know where the queen has gone.” Crewmembers attempted to launch the lifeboats, but the movement and tilt of the sinking ship made this difficult. Many splintered apart or capsized, killing dozens in the process, whereas others could not be pried free from the deck. As it became clear that Lusitania would not stay afloat, those still onboard were forced to jump into the frigid ocean, including mothers with babies in their arms. Once there, they fought to hold onto any piece of wreckage they could find, awaiting the rescue boats that were rushing out from the Irish shore. Three nearby steamers also heard Lusitania’s SOS calls, but they abandoned the idea of a rescue attempt when a lookout on one of them claimed to see a torpedo zoom by. In the end, fewer than 40 percent of those onboard Lusitania survived. They were taken back to Queenstown (now Cobh), Ireland, and given whatever lodging could be found. Some were in such a state of shock that their hair began to fall out, whereas at least two others received amputations without anesthetic. At the same time, local authorities set up three makeshift morgues to handle the corpses being brought in.

The sinking of Lusitania prompted an outcry in the United States (as well as in other Allied countries). “The freely expressed unofficial feeling is that the United States must declare war or forfeit European respect,” the U.S. ambassador to Britain told President Woodrow Wilson the next day. Yet Wilson did not immediately send in the troops, choosing to remain neutral in exchange for a German apology and an end to unrestricted submarine warfare. He even ran for re-election in 1916 using the slogan, “He kept us out of war.” Early the following year, however, Germany sank several U.S. merchant vessels after resuming unrestricted submarine warfare, which it believed would cause Britain and France to surrender in just a few months. Moreover, British intelligence uncovered a telegram from Germany’s foreign minister in which he proposed a military alliance with Mexico. If Mexico entered World War I, the telegram stated, Germany would help it recover Texas, New Mexico and Arizona. Feeling he no longer had a choice, Wilson called for a declaration of war on April 2, a decision that would help turn the conflict in the Allies’ favor. Far from forgotten, Lusitania featured prominently in recruitment posters and war bond advertisements as Americans geared up for battle in Europe.