Grand strategy is more than planning. Planning is necessary: the strategist needs to plan how to mobilise the resources that the strategy requires. He must also plan for the implementation, simultaneously or successively, of the various instruments that he has chosen to achieve his desired ends. The force of habit and the weight of procedure often reduce this to a linear process: budgets are allocated, the means are acquired within that framework, and then put to use in the same way as before, without exploring alternative ways or reassessing the ends. This creates the false impression that whenever the ends are not met, the answer simply is to increase the means or, in military terms, to put more boots on the ground. Such a mechanistic approach leads to unimaginative and hence sub-optimal strategy: ‘ends + ways + means = (bad) strategy’, as Jeffrey Meiser puts in an appropriately formulaic manner. What is missing is creativity: the stroke of the imagination, and occasionally of genius, that will lead the strategist to combine instruments in new ways, or to design entirely new instruments, and to settle on novel ends in order to safeguard the interests of the state. Even a genius has to take into account the available resources, of course; that is why Field Marshal Slim wrote that ‘Imagination is a necessity for a general, but it must be a controlled imagination’. Nevertheless, creativity makes all the difference; that is why strategy is an art as much as a science. In Churchill's words:

‘Instructed judgement’, Churchill says: strategy can be taught – or I would not have written this book – but only up to a point. Since strategy is based on reason, everyone can learn its principles and the method of making strategy, just like everyone can learn how to play a musical instrument.