The revenge is the cause of the war. We can feel it even in our daily life. The first and second wars proved it. The Serbian took the revenge murdering the prince and prince of Austria Hungary. In its return, Austria Hungary declares war on Serbia. All the powers of the world sided the either one. The allied countries blamed and loaded only to Germany for the First World War was as the revenge which couldn't be forgotten by German. As it got its favorable situation, it declared war on the allies. So, we can say the seed of the First World War brought the starting of the Second World War due to the revenge.