The answer is that ww2 started as a result of monarchies struggling for power. This is because Austria and Serbia were competing for the Balkans. Serbia wanted the Balkans because they had a large population of Slavic people and so does Serbia. Austria did not want them to get this land because they didn't want their Slavic population to break away. After a Serbian nationalist killed the Archduke Franz Ferdinand of Austria, Austria declared war on Serbia. Because of secret alliances many more countries joined the war which caused it to be a world war . There were other conflicts that caused this war but this was a direct cause for the war. This is why The Balkans is called the "powder keg" of Europe that's ready to explode.
