It’s been more than a century since world war began, but it continues to shape our lives. It brought us the horrors of trench warfare and lethal new technologies, and left more than 16 million military personnel and civilians dead. It also radically changed the world, with the collapse of the sprawling Austro-Hungarian, Ottoman and Russian empires and the creation of many new ones.

It is easy to blame the horrible decisions made by the belligerents – the countries that went to war – for the outbreak of the conflict, but there are also many big trends that helped push it into full swing. The assassination of Archduke Franz Ferdinand by a Serbian terrorist in June 1914 was just one of them, but it triggered other trends that were already under way.

Among them was the desire by some leaders to build bigger empires. France, Russia and Germany already had empires, but they all wanted to expand them further. This led to secret alliances and tension between the powers. It also led to competition for resources and territory.

As the summer of 1914 unfolded, it became clear that Europe was headed for a great war. The German leadership favored a quick start to the conflict, because they believed that it would allow them to finish unfinished business. This included their support for Austrian attacks on Serbia and a belief that they could use the war to reassert their power and prestige in the world.