We may be living in the closing years of what has been called a “rules-based order”. Countries interact with one another according to rules broadly set after 1945, but the fundamental principles underlying how nation states interact was laid out in the Treaty of Westphalia in 1648, which brought to a close the Thirty Years War. Do not imagine that the world could not return to a pre-1945 understanding, or even worse, to a pre-1648 understanding, of how nation states ought behave.