The Print Collector / Getty Images In the first picture, a man stands near the town hall of Vareddes, France, on March 12, 2014. In the second photo, German troops are taking a rest on the steps of the same building during the first battle of the Marne in 1914. (First photo by Peter Macdiarmid/Getty Images. Second photo by The Print Collector/Print Collector/Getty Images)

Roger Viollet / Peter Macdiarmid / Getty Images The colored photograph shows people walking near the Place des Heros in Arras, France, on March 14, 2014. The black and white picture shows the town hall and the belfry on the square in ruins. (Color print by Peter Macdiarmid/Getty Images. Black and white print by Roger Viollet/Getty Images.)

Gamma-Keystone / Peter Macdiarmid / Getty Images The first photo shows a parked car near the former Episcopal Palace in Verdun, France, on March 11, 2014. The second photo shows a French soldier in what's left of Verdun after a German bombing in 1916. (First photo by Peter Macdiarmid. Second photo by Keystone-France/Gamma-Keystone via Getty Images.)

Topical Press Agency / Peter Macdiarmid / Getty Images In the first image, people stand at Trafalgar Square, London, on March 17, 2014. In the second image, London street urchins dressed as soldiers with paper hats and canes as guns stand in Trafalgar Square in 1919. Behind them is a notice declaring "The Need for Fighting Men is Urgent." (First photo by Peter Macdiarmid. Second photo by Topical Press Agency/Getty Images)

Culture Club / Peter Macdiarmid / Getty Images In the colored image, cars are parked at the former railway station building in Roye, France, on March 12, 2014. In the black and white image, soldiers stand outside the ruins of the railway station in 1917. (Colored photo by by Peter Macdiarmid/Getty Images. Black and white photo by Culture Club/Getty Images)

Apic / Peter Macdiarmid / Getty Images In the first image, traffic runs from the Basilica of Notre-Dame de Brebieres in Albert, France, on March 13, 2014. The second image presents a view of the basilica with the tilted statue of the Virgin after a shell hit the tower in 1915. (First photo by Peter Macdiarmid/Getty Images. Second photo by Apic/Getty Images)

Photo12 / UIG / Peter Macdiarmid / Getty Images The first image shows people walking near the Cathedral in Reims, France, on March 11, 2014. The second image shows the cathedral of Reims during a bombardment in April 1917. (First photo by Peter Macdiarmid/Getty Images. Second photo by Photo12/UIG/Getty Images.)

Lt. J W Brooke / IWM / Peter Macdiarmid / Getty Images In the colored photo, trees surround the Somme canal on March 12, 2014 in Frise, France. In the black and white photo, British solders of the Royal Garrison Artillery working party carry duck-boards across the frozen Somme canal at Frise in March 1917. (Colored photo by Peter Macdiarmid. Black and White photo by Lt. J W Brooke/ IWM via Getty Images)

Maurice-Louis Branger / Roger Viollet / Peter Macdiarmid / Getty Images In the first image, cars are parked near the Place de la Concorde, Paris, on March 12, 2014. In the second photo, German airplanes wrecked by celebrating crowds on the day of the restoration of Alsace-Lorraine are left on the square, Nov. 18, 1918. (First photo by Peter Macdiarmid/Getty Images. Second photo by Maurice-Louis Branger/Roger Viollet/Getty Images)

Paul Thompson / FPG / Peter Macdiarmid / Getty Images The first image shows a gated barrier that runs near Scotland Yard on March 17, 2014 in London, England. The second image shows a large crowd of men responding to a call by the War Office for married men aged between 36 and 40 to become munition workers. They gathered outside the Inquiry Office at Scotland Yard in 1917. (First photo by Peter Macdiarmid/Getty Images. Second photo by Paul Thompson/FPG/Getty Images)