The war that broke out in the summer of 1914 was expected to end quickly, according to the military authorities. Instead, it would last more than four years.
The introduction of new weapons and, in particular, the massive use of artillery at an unprecedented level led to heavy losses for all the main protagonists.
By the time peace was finally established, Europe had lost its role as world leader and it was United States President Woodrow Wilson who put forward the principles for a new international order.