It was the largest amphibious invasion in the history of warfare. On June 6, 1944, more than 150,000 brave young soldiers from the United States, the United Kingdom and Canada stormed the beaches of Normandy, France in a bold strategy to push the Nazis out of Western Europe and turn the tide of the war for good.

In planning the D-Day attack, Allied military leaders knew that casualties might be staggeringly high, but it was a cost they were willing to pay in order to establish an infantry stronghold in France. Days before the invasion, General Dwight D. Eisenhower was told by a top strategist that paratrooper casualties alone could be as high as 75 percent. Nevertheless, he ordered the attack.

Because of bad weather and fierce German resistance, the D-Day beach landings were chaotic and bloody, with the first waves of landing forces suffering terrible losses, particularly the U.S. troops at Omaha beach and the Canadian divisions at Juno beach. But thanks to raw perseverance and grit, the Allies overcame those grave initial setbacks and took all five Normandy beaches by nightfall on June 6.

The first Allied cemetery in Europe was dedicated just two days after the D-Day invasion on June 8, 1944. And since that day, military officials and memorial organizations have attempted to come up with a definitive count of Allied D-Day deaths in order to properly honor those who made the ultimate sacrifice for the free world.

The National D-Day Memorial Foundation is one of those organizations. At its memorial site in Bedford, Virginia, there are 4,414 names enshrined in bronze plaques representing every Allied soldier, sailor, airman and coast guardsman who died on D-Day. That figure was the result of years of exhaustive research by librarian and genealogist Carol Tuckwiller on behalf of the Foundation, and remains the most accurate count of Allied fatalities within the 24-hour period known as D-Day.

John Long, director of education at the National D-Day Memorial Foundation, says that when the memorial was first being planned in the late 1990s, there were wildly different estimates for Allied D-Day fatalities ranging from 5,000 to 12,000. German casualties on D-Day, meanwhile, have been estimated to be between 4,000 and 9,000 killed, wounded or missing. The Allies also captured some 200,000 German prisoners of war.

While military records clearly showed that thousands of troops perished during the initial phases of the months-long Normandy Campaign, it wasn’t nearly as clear when many of the troops were actually killed. In the chaos of the beach landings, for example, some soldiers ended up fighting, and ultimately dying, in different companies. Commanders did their best under difficult circumstances to accurately register the fallen, but death dates weren’t always definitive in the fog of war.

“Their mission was to win a World War against Hitler,” says Long, “not to keep records that would satisfy peacetime researchers 75 years later.”

Tuckwiller began with all of the grave markers at the Normandy American Cemetery inscribed with a June 6th death date. Then she combed through what’s left of WWII military records—many were lost in a fire in the 1970s—looking for “after action” reports from the invasion that included confirmed D-Day deaths.

Something interesting Tuckwiller learned was that the US military would officially declare a soldier dead after he was missing for a full year. So many soldiers who went missing on D-Day—some bodies, for example, were swept out to sea or destroyed in violent plane crashes—had a death date on their military records of June 7, 1945, a year and a day later.

Of course, Tuckwiller couldn’t automatically include all military personnel who died on June 7, 1945 in her record of D-Day fatalities. She needed to confirm that each fallen soldier’s division would have been in Normandy on June 6th. For example, there were men still fighting in Europe and the Pacific in 1945, so those names had to be scrubbed.

Long knows that the Foundation’s list isn’t complete, but says that it’s the best figure that we have to date. Of the 4,414 Allied deaths on June 6th, 2,501 were Americans and 1,913 were Allies. If the figure sounds low, Long says, it’s probably because we’re used to seeing estimates of the total number of D-Day casualties, which includes fatalities, the wounded and the missing.

While casualty figures are notoriously difficult to verify—not all wounded soldiers are counted, for example—the accepted estimate is that the Allies suffered 10,000 total casualties on D-Day itself. The highest casualties occurred on Omaha beach, where 2,000 U.S. troops were killed, wounded or went missing; at Sword Beach and Gold Beach, where 2,000 British troops were killed, wounded or went missing; and at Juno beach, where 340 Canadian soldiers were killed and another 574 wounded.

The vast majority of the men who died perished in the very first waves of the attack. The first soldiers out of the landing craft were gunned down by German artillery. Once those pillboxes were destroyed and the machine guns silenced, the later waves of troops faced far better odds.

Among the stunning losses of those first-wave soldiers were 19 young men known as “the Bedford Boys.” The U.S. Congress chose Bedford, Virginia as the site of the National D-Day Memorial because it suffered the highest per capita D-Day losses of any community in the nation. The 19 Bedford Boys were mostly National Guardsman who were some of the first to land on Omaha beach.

“As a result, their losses were just staggeringly high,” says Long.

Two decades after the National D-Day Memorial Foundation began its search for the D-Day fallen, another name was recently added to the bronze plaques. On Memorial Day 2019, the Foundation announced the addition of John Onken, a German-born soldier who was likely one of the first to die for his adoptive country during the seaborne phase of the D-Day invasion.

At 4 a.m. on June 6th, Onken and his fellow U.S. Cavalry troops were tasked with clearing two small islands off the Normandy coast of possible Nazi gun positions or enemy lookouts.

“They didn’t find any Germans, but they did run into mine fields,” says Long. “Two men were killed and one of them was John Onken.”

In addition to earning his rightful place on the National D-Day Memorial wall, Onken’s name is included in a new book commemorating the 75th anniversary of D-Day called We will Remember Them: An accounting of the D-Day Fallen, published by the National D-Day Memorial Foundation.

“We’re continuing the search for other names,” Long says. “We’ve never considered this a finished project.