Over the course of World War I, more than 1 million French soldiers were killed in the line of duty. From 1914 to 1918 as the war raged on, war photographers documented life on the front lines. And, for the first time, they captured color photographs that, when viewed today, bring the struggles of these soldiers to life.

While photographers like Mathew Brady, who documented the American Civil War, had pioneered war photography, his static black and white photos make it difficult to relate to his subject. Instead, the French army employed new technology to give color to their work. In 1903, French brothers Auguste and Louis Lumière patented an early color photography technique—autochrome. Although autochrome was the first commercially successful color photography process, it wasn't until Kodak developed Kodachrome color film in 1935 that color photos became commonplace.

Even with the widespread familiarity of color film, only 50% of American newspapers were using color by 1983, which makes it all the more jarring to see the vast collection of color photos taken by the French Army. Primarily shot by army photographer Paul Castelnau, the rich archive covers everything from life in the trenches to portraits of nurses and doctors. The color, still fairly vivid, is a striking reminder of the men and women who sacrificed during this important period in history.

These color photos document life in the French army over the course of World War I.

Army photographers used the still fairly new autochrome technique to bring color to their photographs.