The conqueror and conquered peoples always remain in a state of war with one another, unless the nation, returned to full liberty, were to choose voluntarily its conqueror as leader.
Gist of Idea
A state of war remains after a conquest, if the losers don't accept the winners
Jean-Jacques Rousseau (Discourse on the Origin of Inequality , Part II)
Tricky if part of the conquered nation accepts the conqueror, and the other part doesn't, as in France in 1940. In a permanent conquest the state of war seems to fade away, as in England in 1066.
Rousseau,Jean-Jacques: 'The Basic Political Writings', ed/tr. Cress,Donald A. [Hackett 1987], p.71