Rarely has a state safeguarded its vital interests by passively waiting for things to come. As A.J.P. Taylor wrote: ‘Those who really know what they want, get it – not necessarily of course in the way that they want, but they get it somehow. But those who hesitate between different objectives and seek only some compromise which will postpone difficulties, get nothing – not even the postponement they long for’. A state may, of course, adopt a defensive grand strategy in the face of current and expected threats and challenges. Or it may opt for an offensive approach, grasp the initiative, and seek to change its environment. Either way, be it for offence or for defence, a state must prepare to act: those that are not proactive will be forced to react to the strategic moves of the others. In war, if one can get into the decisionmaking cycle of the enemy, that is make the next move before the opponent has even had time to digest and react to the previous move, success is nearly always guaranteed. In 1940, French command and control was methodical, but slow, geared to the speed of operations of the First World War. As a result, France was systematically outpaced – rather than outgunned – by the German armoured formations. The American armed forces achieved a similar feat against their Iraqi counterparts in the two Gulf Wars, in 1991 and 2003. The same rule applies to grand strategy overall: the state that holds the initiative and sets the pace has the advantage over the others. Vice versa, once stuck in a reactive mode, it is difficult to focus on one's own ends.

The very definition of a great power implies proactivity: the ambition to have a global impact cannot be realised otherwise. Proactivity should not be mistaken for aggressiveness, however: rather than in undermining or attacking its rivals, a power can also be proactive in forging alliances and partnerships, and in improving its own competitiveness. Setting out a constructive agenda in the mutual interest of various powers takes as proactive an approach as launching a military intervention. If, however, the great powers ignore the opportunities for cooperation and focus exclusively on competition and rivalry, they risk bringing about a world ruled only by Thucydides’ dictum: the strong do what they will and the weak suffer what they must.