The world’s largest militaries spent a great deal of time and effort preparing for war. These preparations led to a huge arms race that caused countries to get into competition for power.

As a result of this arms race, the world was brought into conflict in 1914. The assassination of Archduke Franz Ferdinand of Austria set off the chain reaction that led to the war.

Imperialism was another cause of the war. Germany and Britain both had empires and wanted to expand them even more. This was very dangerous because it created tension and rivalry between the countries. Nationalism also played a role. It made people decide which country to be loyal to based on their ethnic or cultural background. This was very dangerous because it caused countries to fight over territories and resources, leading to war.

Almost all the belligerent nations had conscript armies. These required three to four years of service from able-bodied men of military age. This meant that there were a lot of young men ready to fight for their country. In addition, the Allies had a number of volunteer units. These units were a much smaller force than the conscripted armies.

During the first two weeks of battle, British artillery fires 4,283,550 shells at the German lines near the city of Passchendaele. As a result, the Allies gained a slight advance. But the Germans were able to hold the Allied line. This battle marked the beginning of trench warfare and led to a long and bloody campaign.