Respuesta :

Countries were confident that allies would fight with them if they declared war.

Europe had developed a system of alliances that divided the  continent in two. Democratic Britain and France, along with the Russian  Empire, had formed the Triple Entente. Central Powers were comprised of the  new German Empire, Austria-Hungary, and Italy. The assassination of the heir  to the Austro-Hungarian throne by a Serbian nationalist triggered the world  war in August 1914.