The long and miserable history of armed conflict has seen wars kicking off for dozens of different reasons. Independence, territorial disputes, cultural differences, religion, philosophy, or just living next to each other for too long have all got presumably sane and rational people to grab the nearest killing implement and attempt to mutilate each other in the biggest numbers possible.
It seems impossible for humans to live in groups that identify as nations without wanting to start throwing hands at someone else.
There are times in history when two groups of aggressive people just couldn't be bothered to think that deeply. They really, really wanted to have a war and seized on the first available excuse to get rucking, no matter how lame or bizarre that excuse might be.
Either that, or they were so hyped up and kill-happy that all it took was some innocuous trigger event to get the tanks rolling across that border.
The wars that followed owed their existence at least partially to some very stupid reasons, which would all be hilarious if so many people hadn't died.