Before sunrise on June 28, 1914, a pack of cyclists set off from Paris on the 12th Tour de France. Hours later, an Austrian archduke stepped out in Sarajevo and was assassinated in the street, igniting the carnage of World War I.

Now, 100 years later, cycling's greatest race is paying special tribute to the millions who fought and died in what came to be known as the Great War. Several stages of the Tour de France will run this year along the war's killing fields, trenches and fronts in northern France and Belgium.

The 1914 Tour was the last before a five-year suspension due to the war. Of the 145 riders that day, 15 of them, including three Tour champions, would die in the fighting.

In all, an estimated 45 cyclists who had raced in pre-war Tours were killed in the 1914-1918 conflict, according to cycling historian Jean-Paul Bourgier.

The Tour itself has a complicated history with the war. Its founder, Henri Desgrange, joined in the warmongering, using his L'Auto newspaper to issue a lusty call for his countrymen "to go get those bastards".

"When your rifle butt will be on their chest, they will ask you for forgiveness. Don't let them trick you. Pull the trigger without pity," Desgrange said, according to Graham Healy's book The Shattered Peloton.

After the war, Desgrange pledged to never let a German rider compete in the Tour, a threat that was never carried out.

This year's three-week Tour begins on July 5 in Leeds, England, before crossing the English Channel three days later. Riders and fans will have several occasions to pay homage to war victims: Stages 5 through 10 largely trace the 645-km-long Western Front, from Ypres, Belgium, to the Swiss border near the northeastern French city of Mulhouse.

An estimated five million combatants died on this front during the war, the British government estimates. Most are still buried there in immaculately landscaped military cemeteries or under farmers' fields in unmarked graves.

Stage 5 starts in Ypres, the killing ground immortalized by Canadian soldier-poet John McCrae in his poem In Flanders Fields:

"We are the Dead. Short days ago

We lived, felt dawn, saw sunset glow,

Loved and were loved, and now we lie

In Flanders fields."

Riders will assemble that day within sight of the Menin Gate, a memorial dedicated to the 54,405 British and Commonwealth casualties whose graves are not known.

Not far from the Stage 5 start is cycling's iconic Kemmelberg Hill. As recounted by Healy, Frenchman Camille Fily, at 17 the youngest Tour rider, was shot and killed around there late in the war while serving as a bike messenger. Among the many nearby war memorials is the Kemmelberg French Ossuary, where the bodies of 5,294 French soldiers lie buried.

The Stage 6 start in Arras takes riders near France's largest military cemetery, Notre Dame de Lorette, where 40,058 French war dead are buried. Among them, most likely, is 1909 Tour champion Francois Faber of Luxembourg.

Less than a month after finishing ninth in the 1914 Tour, Faber enlisted in the French Foreign Legion. He was killed the following May during the Battle of Artois, just north of Arras. His body was never found, but a plaque in his memory can be seen in the Notre Dame de Lorette church.