The Merchant Marine suffered the worst losses of World War II

It may sound crazy, but an organization suffered worse losses in World War II than the Army, the Marine Corps, or even the Navy that was in charge of guarding it: The Merchant Marine, the sailors who crewed ships carrying goods from U.S. factories to European battlefields, lost nearly 4 percent of its members in the war.

Merchant Marine officers and crew members were in high demand in World War II, but it was a dangerous and largely thankless service.

(National Archives and Records Administration)

The Merchant Marine was never designed for front-line combat on the battlefield or on the ocean. It's made up of mostly civilian members who conduct almost any type of maritime trade in peacetime, from fishing tours to oil shipping. During a war, the federal government can make these sailors into an auxiliary of the U.S. Navy.

And during World War II, these men went through light training before crewing ships that had to brave not only the seas and storms, but German U-boats that were organized into wolfpacks and ordered to hunt the Merchant Marine.

This forced these men into the worst of the fighting, despite their largely non-combat role. And it made sense for both sides. Logistics moves supplies and, along with the industry that creates those supplies, wins wars. Germany had a weak industrial base and needed to keep American industry out of the war as much as possible. But one of America's greatest roles in the war was that of "Arsenal of Democracy," and it couldn't afford to keep the Merchant Marine at port.

German U-boats sank ships flying under Allied colors and didn't have the ability to recover and rescue the people imperiled by the sinking.

(Willy Stower, public domain)

And so German U-boats patrolled the American coasts, sinking ships — sometimes within view of their ports. Whenever possible, German U-boats operated on the surface, drawing oxygen to run their diesel motors and attacking with deck guns that could punch holes in ships' hulls and doom them. When that was too dangerous, they would hunt underwater and attack with torpedoes.

For the sailors of the Merchant Marine, this was terrifying. They were under threat of German attack from the moment they left the range of the shore guns until they reached European ports. American waters were actually some of the most dangerous as U-boats hunted the coast at night, looking for U.S. ship silhouettes blocking out lights from shore. Once they had the target, the subs could attack and disappear.

Counting the waters around the American Philippines, Alaska, and the Gulf of Mexico, the Merchant Marine lost approximately 196 ships in U.S. waters. Meanwhile in the Caribbean, our backyard, we lost another 180 ships. Officially, the U.S. lost 1,554 ships in the war. Approximately 8,000 to 12,000 Merchant Marine sailors were killed.

A ship sinks during World War II.

And the situations during the sinkings were terrifying. When ships were struck, sailors would have only minutes or seconds to get off the boat and to safety. Fires and the twisted hull could block passageways and make escape impossible. Jump into the water too early from too high and you could die from striking the water. Wait too long and the suction of the ship would pull you under to drown. Sharks, oil fires, and starvation could kill even those who made it out safely.

And, oddly enough, since the crews were often still technically civilians even when under Navy control, their pay stopped whenever they weren't actively serving on a ship. That included when the ships were sunk under them and they had to spend weeks trying to reach a safe port.

The worst year, by far, was 1942, when approximately 500 ships were lost or captured in a single year. When the U.S. and the Axis Powers exchanged declarations of war in December 1941, U.S. ships sunk or otherwise lost skyrocketed from an average of 1 per month from January to November to about 55 in December, not counting Navy warships destroyed at Pearl Harbor.

"Victory" and "Liberty" ships under construction during World War II. These ships allowed American arms and supplies to be shipped en masse to Africa, Europe, and the Pacific.

(War Shipping Administration)

The U.S. rushed the convoy system from World War I back into service. Merchant ships were encouraged to sail in planned convoys with U.S. and British naval escort, and ships that took part were much safer than those who went it alone. Less than 30 percent of U.S. and allied ships lost to U-boat attacks were in a convoy while they were sunk.

This was due to a number of factors, the darkest of which was that, even when U-boats had the edge against Navy vessels, they needed to remain underwater. Since they couldn't use their deck guns without surfacing, that meant they could only sink as many ships as they had torpedoes.

But British technological advances and the large American industrial base began giving potent sub-hunting weapons to the U.S. and Allied navies and, suddenly, the U-boats had a lot more to worry about when facing convoys than just their limited arsenals. By May, 1943, sonar, radar, improved depth charges, and other tools had tipped the battle in the Atlantic and across most of the oceans.

An illustration of the sinking of the Lusitania commissioned by the London Illustrated News. The ship was sank by U-boats, leading to America's direct involvement in World War I.

(London Illustrated News)

Subs were on the run, and the Merchant Marine could sail with less worry. Still, the Merchant Marine lost between 9,000 and 12,000 sailors during the war, depending on whose numbers you use. The National World War Two museum puts the number of dead and presumed dead at 11,324, a loss rate of almost 4 percent. Meanwhile, the Marines took losses of almost 3.7 percent with 24,500 killed out of 669,000 people who served throughout the war.

Yes, joining World War II as the crewman on a merchant ship was more dangerous than joining as a Marine, and the Marines had it the worst of all the Department of Defense branches in the war, suffering 10 percent of all U.S. casualties despite being only 5 percent of the total force.