When European nations squared off against each other in the summer of 1914, it’s doubtful that anyone envisioned it would mushroom into a four-year-long conflict that would be vastly more lethal than any previous war on that continent, both for military personnel and civilians.

Major powers such as Britain, France, the U.S. and Germany kept detailed records of the war’s human cost. But the carnage of World War I was so extreme and pervasive, and involved soldiers and civilians from so many different nations, that historians have had a difficult time agreeing on exactly how many people lost their lives.

“It’s hard to say,” says Michael Green, an associate professor of history at the University of Nevada, Las Vegas. He notes that some estimates—but not others—have included deaths from the 1918 flu pandemic and the Armenian genocide committed by Turks of the Ottoman Empire, events which overlapped with the war and were intertwined with it.

Higher Toll Among Allied Forces

A 2011 report by the Robert Schuman European Centre pulled from government records and research by the Carnegie Endowment for International Peace estimated that slightly more than 9.7 million military personnel from more than two dozen nations lost their lives, plus more than 6.8 million civilians who died from causes such as starvation and genocide. In all, about 16.5 million people died.

According to the report, the victors of the war suffered more military deaths than the losers. The Allied side, including Britain (885,138 deaths), France (1,397,800), Russia (1,811,000), Italy (651,000), Serbia (275,000) and the U.S. (116,708), in addition to a host of other nations—lost 5.4 million military personnel. 

That’s considerably more than the approximately four million military members lost by the Central Powers, which included the German Empire (2,050,897), Austria-Hungary (1,100,000), the Ottoman Empire (2,150,000) and Bulgaria (87,500). Those totals include both combat-related deaths and fatalities from accidents, disease and the ordeal of being held as prisoners of war.

The actual death toll may have been even higher. As French anthropologist François Héran notes, France’s “implausibly precise” official death toll of 1,357,800, for example, probably was closer in reality to 1.5 million. 

Advanced Warfare Exacts Heavier Death Tolls

Why did so many soldiers and other military members lose their lives? One reason is that, compared to previous conflicts, “warfare had become more technologically advanced,” Green explains. “World War I was the first with trench warfare, large use of submarines and airplanes, and poison gas, as well as flamethrowers and machine guns.”

Particularly at the start of the war, military tactics and strategy didn’t take into account the advances in killing technology. As French historian Antoine Prost notes in the 1914-1918 International Encyclopedia of the First World War, infantry trained to use obsolete tactics would charge across open fields at artillery and machine guns, resulting in massacres.

According to Prost, during the first four months of the war alone, the French Army lost 310,000 soldiers, leading a then-young Lieutenant named Charles de Gaulle to later write that “In an instant, it appeared that any bravery in the world could not prevail against firepower.” (De Gaulle survived to become France’s leader in exile during World War II, and eventually served as French President from 1959 to 1969.)

On this new, terrifying sort of battlefield, the biggest lethal threat was death inflicted from a distance by artillery shells. According to Prost, 60 percent of wounded French soldiers were injured by artillery shells, compared to 34 percent from bullets and 6 percent from bayonets and other causes. 

The inability of either side to quickly win the war also exacerbated the death toll. It led to brutal, protracted struggles such as the Battle of the Somme, which lasted from July to November 1916. As both sides pounded each other with firepower in a relatively small 18-mile stretch along the Somme River in France, 20,000 British soldiers were killed on the first day of the fighting alone.

Infections, 1918 Pandemic Spread

Along the Western Front, where the two sides were mired for years in brutal trench warfare, the heavily manured soil contributed to the death toll, by encouraging the growth of tetanus and gas gangrene that killed injured soldiers, according to the Imperial War Museums.

The war also made the 1918 influenza pandemic even more deadly. The flu spread rapidly among American soldiers as they gathered in training camps and traveled across the Atlantic to ports such as Brest, France. It continued to surge as they went into battle. In October 1918, as U.S. soldiers fought the Germans in the Meuse-Argonne offensive, 1,451 Americans died from the flu. In the course of the war, the pandemic killed a total of 45,000 American troops and 14,000 Germans, and as many as 100,000 soldiers on both sides, according to Dutch medical researchers Peter C. Wever and Leo van Bergen.

The prolific slaughter continued right up until the war’s final days. Even after German, British and French officials gathered in a railroad dining car north of Paris in the early morning hours of November 11, 1918 and signed an armistice, a six-hour delay in the end of the fighting—intended to provide time for the news to reach the front lines—cost the lives of nearly 3,000 more soldiers. Those final casualties included an American, Sgt. Henry N. Gunther, who charged a German machine-gun nest and was shot to death just one minute before peace officially came.

Even soldiers who survived World War I may have had their lifespans shortened by the conflict. Though only 2 to 3 percent of soldiers exposed to mustard gas on the battlefield lost their lives, the rest may have been at higher risk of developing cancers later in life, as military writer James Patton notes.

A 2014 study of soldiers from New Zealand soldiers who served in World War I found that war survivors, about 40 percent of whom had been wounded, had a life expectancy that was 1.7 years shorter than a group who hadn’t been sent into combat. They also had a higher suicide rate than civilian men in their age group, suggesting that exposure to the war’s horrors had taken its own heavy toll.

HISTORY Vault: World War I

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