A great power is a state that possesses a reputation for existing or latent military strength that may be equalled but not significantly surpassed by that of any other power. It is, in other words, a power of the first rank in terms of reputation for military strength, or military ‘prestige’. Such powers have always taken the lead both in shaping and enforcing international law, as well as the less formal rules of the system of states such as those defining spheres of influence. They are therefore the central pillar of world order (which means a condition governed by rules) and, to the extent that they act in concert, the nearest thing that the states-system has to a ‘government’. In the twentieth century this has been explicitly recognised by allowing (as if this could be prevented!) the great powers a privileged position in the international organisations charged with maintaining international peace and security, since 1945 the United Nations. Who are they? What interests pull them together? Has the operation against Iraq in 1991, in which three of the major powers, with the blessing of the UN Security Council, played such a prominent role, ushered in a ‘new’ world order? First, however, a little history.