European nations were always hostile to a certain extent to each other in the past centuries, while not all were hostile to each other at the same time, there were skirmishes going on a lot of the times, together with political and economical schemes being present.
However, this changed importantly with the rise of nationalism that favoured the right of self-determination and independence of each individual nation. This, coupled together with militarism, increased the rivalries that were already present in Europe due to historic reasons.
