There is no doubt that if war has to cede to peace, a certain logic of war-ending has to be followed. It is well-known that Grotius did distinguish a right to war and a right in war. Can we also consult Grotius to articulate the right of war-ending? Is there a "ius post bellum" in Grotius? This question is the more important since Grotius, one of the architects of the 'Westphalian system', has a very clear eye, not only for what might - justifiably - divide nations, but also what unites nations.