Making decisions on grand strategy takes courage: vital interests are at stake, so the consequences of failure may be grave, especially if one is engaged in active rivalry with another power. This is a different kind of courage than gallantry on the battlefield, of course; it is the courage to take responsibility, which is a requirement for strategic success, as Sir Hew Strachan notes. Every decision is based on imperfect information, and one can never fully know the intentions of the other powers – the fog of diplomacy is as real as the fog of war. Accepting a degree of risk is inevitable, therefore, or one would never make any decision – and indecision and inaction have consequences too. The French and British policy of non-intervention in the Spanish civil war (1936–39) in practice amounted to a weakening of the legitimate Republican government, for Italy and Germany did militarily support Franco's rebellion, and London and Paris had no intention of stopping them. In such cases one must agree with Talleyrand, who defined nonintervention as ‘a metaphysical and political term that means more or less the same as intervention’. Sometimes, of course, not acting really is the best course to take. But not acting must be a conscious decision, because one assesses that one's interests are not sufficiently at stake to warrant action; it must not be the result of inertia or mere risk aversion.

In grand strategy avoiding failure is not necessarily the same as success. By escaping from the European continent through Dunkirk, the UK between 26 May and 4 June 1940 narrowly avoided the destruction of the British Expeditionary Force. That was justifiably celebrated as a remarkable achievement, but as Churchill dryly remarked: ‘Wars are not won by evacuations.’ Real success means achieving one's ends, which one must define in a sufficiently ambitious way to safeguard one's interests in the first place. That end, in 1939, had been to defeat Germany and restore the independence of Poland; instead, by sitting tight in defensive positions during the ‘phoney war’ and leaving the initiative to Germany, France and the UK invited failure.