In 1914, Germany could mobilize about 4.9 million men (of which 4 million were mobilized and carried the Army through 1917) from a population of about 67 million. When war was declared, many men joined early. In 1914, huge numbers of volunteers of all ages came forward and were accepted. 1915 did not produce as many, and after that, only about 5% of eligible males volunteered.
In England when war broke out, men also rushed to join, and over one million men had volunteered to fight by December 1914. By the end of the war, almost one quarter of the total male population had served in the armed forces.
Gallery: Remembering the First World War: Front Line