This book began with the assertion by the High-Level Panel on Threats, Challenges and Change that a common understanding on the use of force is necessary for revitalising the role of the United Nations in the twenty-first century. The most lethal force known to mankind so far is nuclear weapons. As the above quotes show, the subject of nuclear arms control and disarmament is back on the international agenda with a vengeance. The triple crisis arises from non-compliance with obligations of the Non-proliferation Treaty (NPT) by some states engaged in undeclared nuclear activities and others that have failed to honour their disarmament obligations; states that are not party to the NPT; and non-state actors seeking to acquire nuclear weapons.