Even history buffs are stumped by this one. What single battle in our military history killed more Americans than any other?

It wasn't the Civil War's Gettysburg, where Americans died on both sides of the battle lines. It wasn't the notorious Battle of the Bulge, when Germany broke out with an offensive late in World War II. It wasn't D-Day.

It was a month-long battle in World War I -- the Battle of the Argonne Forest that claimed 26,277 American lives and left 95,786 wounded, astronomical figures compared with battles today. It took an entire campaign to take Normandy in World War II to amass more American dead.

So what does it mean that we don't even recall it?

It seems the war has slipped from the minds of Americans, even though this year marks the 100th anniversary of the United States entering it.

The saddest thing about Meuse-Argonne, also known as the Battle of the Argonne Forest, is that "the times I've been to the cemetery, there's been no one there," says Andy Wiest, distinguished professor of history at the University of Southern Mississippi. "People have just forgotten it. Go to the D-Day cemetery in Normandy and it's always crowded.

"They've forgotten about WWI in general. Go out on the streets of Gulfport or Biloxi and ask what the most costly battle in U.S. history was, and no one will come up with that. It's sad, but you pretty much have to be a specialist to know it. That's how far WWI has slipped from our memory and imagination."

WWI in Gautier

The last veteran of that war died in 2011, and he was 110, so "there's no living memory of that war," said John McAnally, Mississippi Gulf Coast Community College history teacher.

It has become our grandfather's and great-grandfather's war, he said.

Another fact about the so-called Great War is that every state sent soldiers.

Ocean Springs has a monument to one of its own who died there. The G.I. Museum in Gautier has acquired artifacts -- dug from the trenches of France at the Battle of the Somme -- for a special display this year.

America was invested, though not nearly as heavily as Europe and Great Britain, whose residents trekked to battlegrounds and cemeteries on their 100th anniversaries last year. All of England marked the Battle of the Somme, the deadliest single battle in British history.

We entered the war in 1917, so this would be the year to visit the Gautier museum and see what pieces of history are available.

The 100-year-old French helmet on display there seems small and fragile compared to ones today.

Unlike the American helmet that could adapt to different head sizes with a sweat band, France made different-sized helmets for its soldiers, which was a logistical nightmare, said Doug Mansfield, who co-owns and operates the G.I. Museum with his wife, Cheryl Mansfield. Soldiers couldn't pick up someone else's helmet and use it on the battlefield.

The museum also has WWI medals, ammo pouches, belts, canteens, gas masks and several uniforms -- one that belonged to John Ripley Walker of Ripley, Mississippi. His son, who flew B-17s in World War II, donated it.

Americans didn't have special uniforms for different branches like the Germans did. They had insignias that told the branch of service -- infantry, artillery, air corps, medical corps, Mansfield says.

The museum recently acquired a candle holder from the German trench line and a carbide lamp that burned pellets to give off light.

"They didn't have lights like we do today, not even a flashlight," Mansfield said.

Camp Shelby was opened in 1917, Mansfield said.

"We have WWI postcards from there and letters written from soldiers at Camp Shelby. There's one dated Dec. 1, 1918, that starts 'Dear Mom' ...

"We have a postcard sent home Nov. 10, 1918 from a soldier saying he was captured by the Germans and was in a camp. The war ended on Nov. 11, 1918, the day the Armistice was signed."

What it was like

The United States entered the war in April 1917 and by June of 1918, little more than a year later, it had raised an army of nearly 3 million -- equipped and trained soldiers on the ground in Europe.

It's something other countries probably couldn't do, Wiest said.

Wiest is director of USM's Dale Center for the Study of War and Society, which the university says is one of the top military history programs in the country. Dale Center faculty have served as documentary consultants and experts for the History Channel, the Military Channel, PBS, Lucas Films and the BBC.

The Battle of Meuse-Argonne began in September 1918 as the war was drawing to a close. The fresh U.S. troops attacked a well-fortified German trench line.

"It was a different kind of war for us," Wiest said. "The war we were used to was open maneuvering, an army moving about the countryside. WWI was a siege like Vicksburg (from the Civil War) that straddled an entire continent. You couldn't go around the trenches, you had to plow through them. There was no subtlety. Battles were won by brute force."

German trench lines formed a web of fortifications. There would be a front line and then a second trench line with a fort and then another and another, connected with underground tunnels that continued inland for 7 or 8 miles.

"You had to ball a fist and try to bust your way through the trenches, which meant a heavy artillery fire," Wiest said. "French, German and British armies had been getting on-the-job training for four years. They had fought a number of battles like the Meuse-Argonne. We were new."

More than 1 million Americans fought in that single battle, "a battle that lasts for a month, crawling forward literally from your shattered front-line trench to their shattered front-line trench," Wiest said. "And these guys are fighting in hell -- landscape devastated, no food, no one stopped to bury any of the dead.

"The capacity for saving the wounded was low in WWI. It takes a long time to die and the battlefield is loud with the dying. It's a special kind of horror that these men had to fight through. Everything you heard bad about Vicksburg, multiply it 10 to 15 times."

Both mustard and phosgene gases were used at Meuse-Argonne, one causing internal and external blisters. The other had soldiers coughing up pieces of their lungs.

Making of a world power

The war, however, ushered America into the role of a world power.

When Wiest teaches World War I in class, he calls it the beginning of the American century.

It was a fight about dominance in Europe, he said, but in the end, the country that mattered was the United States.

The European powers had beaten themselves to death for five years, he said. "When it was over, we're rising, taking their markets."

"Britain begins that war as the leading lender, the world's bank. Then it spent every nickel and went into debt to us. America steps onto the world stage. After the war, we matter.

"In that sense, it may be the most important war America ever fought because we're still that super power.

"Before World War I, if you made a move in the world, you asked Great Britain if it was OK. After the war, you checked with us."

We were suddenly recognized as a power to be reckoned with, and it's been that way ever since.