By January 1916 the war had become a stalemate. Millions had died and yet no side had achieved a decisive breakthrough. Austria-Hungary tripled the size of its armies to five million men. Germany doubled its forces to seven million. And in Britain men were volunteering to fight at the rate of up to 33,000 a day.
The numbers will favoured one side, then the other in 1918. When the Bolsheviks took Russia out of the war, millions of German and Austro-Hungarian troops were freed up to attack Britain and Belgium, France and Italy. But across the Atlantic, America was training an army of two-million men.