A collection of glass plates from an unknown photographer shows the daily life of soldiers and military leaders.

British army Field Marshal Horatio Herbert Kitchener, second from left, meets French Gen. Albert Baratier, on horseback, with French Marshal Joseph Joffre, on the Champagne front, in eastern France in 1915. A viscount in the Armored Cavalry branch of the French army left behind a collection of hundreds of glass plates taken during World War I that have never been published. The year 2014 marks the 100th anniversary of the start of World War I. Collection Odette Carrez/Reuters