In August 1914, Europe's major powers threw themselves into war with gleeful abandon. Germany, a rising power with vast aspirations, plowed across Belgium, seeking to checkmate France quickly before Russia could mobilize, thereby averting the prospect of a two-front war. Thousands of young Germans, anticipating a six-week conflict, boarded troop trains singing the optimistic refrain: "Ausflug nach Paris. Auf Widersehen auf dem Boulevard." ("Excursion to Paris. See you again on the Boulevard.")

The French were eager to avenge the loss of Alsace and Lorraine to Germany in 1870. The British government, leery of Germany's growing power, mobilized hundreds of thousands of young men to "teach the Hun a lesson." Across the continent, writes British historian Simon Rees, "millions of servicemen, reservists and volunteers ... rushed enthusiastically to the banners of war.... The atmosphere was one of holiday rather than conflict."

Each side expected to be victorious by Christmas. But as December dawned, the antagonists found themselves mired along the Western Front – a static line of trenches running for hundreds of miles through France and Belgium. At some points along the Front, combatants were separated by less than 100 feet.