People _do_ just wake up one day and decide some piece of land should belong to them, or that they don't have enough money and can take yours, or they are just sick of looking at you and want to be rid of you. They will have some excuse or justification, but really they just want more than they have.
People _do_ just wake up and decide to be evil.
A nation that might fit this description may have had their populace indoctrinated (through a widespread political campaign) to believe that the majority of the world throughout history seeks for their destruction. That's a reason for why they think that way, but not because they woke up one day and decided to choose violence.
However not a justification, since I believe that what is happening today is truly evil. Same with another nation who entered a war knowing they'd be crushed, which is suicide; whether that nation is in the right is of little effect if most of their next generation has died.