Answer: It really depends on the standpoint.
Explanation: From the international relations standpoints, wars are justified. Countries will go to war when the problem of war is the problem of bargaining over objects that are of value for more than one state. Sometimes States (or countries) don't have anything else to lose and they'll just go on war to see if they can win something, while other countries will go on war because they know that they are more powerful. Wars might happen for many reasons, but the most common ones are territory, policies, state mistreatment of its citizens, policy change, regimes, or combinations of multiple conflicts.
However, if you look at it from a historical standpoint or maybe even a social studies, wars are never the answers because it's usually a group of men who decide that they have to go on war, a lot of innocent people die, and they don't really have reasons to do it, especially when it pertains to wars caused by ethnic/racial/religious issues.