The strong do what they have to do and the weak accept what they have to accept.
Thucydides says this about the brutality of the world and its anarchic order in which the only thing that matters is the power you have. This power is what you either use to your benefit or you suffer by others who have it.
War is an evil thing; but to submit to the dictation of other states is worse... Freedom, if we hold fast to it, will ultimately restore our losses, but submission will mean permanent loss of all that we value... To you who call yourselves men of peace, I say: You are not safe unless you have men of action on your side.
Thucydides in this quote talks about the necessity of war. War is the only solution to keeping the peace and it is inevitable. This resonates deeply within the realist branch of international theory.
Be convinced that to be happy means to be free and that to be free means to be brave. Therefore do not take lightly the perils of war.
Happiness is freedom, and freedom is won through war. This has been many a reason for nations to go to war. War is a means to an end and Thucydides sees it as well worth it. Freedom in this way is seen as a human need if happiness is wanted. The other option here would probably be slavery.
