Berlin Joins the War a soldier don the pickelhaube (b/w photo)

Shortly after the assassination, Austria-Hungary issued a list of demands to Serbia, demanding they halt all anti-Austro-Hungarian activity, dissolve certain political groups, remove certain political officers, and arrest those within its borders who participated in the assassination, among other things -- with 48 hours to comply. Serbia, with the backing of their ally Russia, politely refused to fully comply, and mobilized their army. Soon after, Austria-Hungary, backed by their ally Germany, declared war on Serbia on July 28 1914. A network of treaties and alliances then kicked in, and within a months time, Germany, Austria-Hungary, Russia, France, Britain, and Japan had all mobilized their armies and declared war. In this photo, taken in August of 1914, Prussian guard infantry in new field gray uniforms leave Berlin, Germany, heading for the front lines. Girls and women along the way greet and hand flowers to them.