How did leadership cause World War 1?

Answer 1

The countries that were the primary combatants of World War 1, started building their military long before the war started. These countries were rivals and if one country expand their military, then their rival would do the same. After some time these countries had large enough militaries of their own to start a war.

Answer 2

leaders were donkeys that lead lions into fertile battles they were all arguing until something sparked the war the death of an arch bishop the next king