Answer: Hopefully I can explain this well.
Step-by-step explanation:
During the era of WWI, tensions were already running rampantly high amongst the European countries. Many countries in Europe were forming alliances, backstabbing each other, and spying on one another; plotting assassination attempts of rival European monarchs.
As a result of this tension between European countries, neighbors began to militarize their countries. Militarize means “to build up strength in armies”. Many of these nations began militarizing, in belief that an emminate war was going to break out. All chaos broke loose when Archduke of Austria (I think) was assassinated in Sarajevo, leading to the first WWI.
I hope this helps.