It is very hard to say if it can be justified, but we can do some research and get some ideas.
For example, after WW1 Germany was very limited and dying slowly because of the Treaty of Versailles. They had a gigantic debt, they couldn't have an army (so they had no defense), the country was divided, and some other consequenses. So we could maybe say that a war comes when:
The country has to pay an unfair debt: they would never prosper because of the debt.
The country in defenseless and has to obbey to an unfair Treaty: As the Treaty of Versailles.
The country needs to fight in order to recover something that belongs to it and it is 100% necessary to survive: this one is very subjetive, and hard to analyze.
The country has been enslaved by foreigner forces: if a country lost its identity, the people could riot.
The country has been constantly opressed by foreigner people due to its form of government: as USA vs. N. Korea (both critizice each other because their form of government).
The country depends on foreigner issues in order to survive: a country with a fake independence.
Anyways, as I said before, it is very hard to tell and it depends on many factors.
Maybe you could help me with 1 click in vote, pls.