I’m not saying that modern war is like a video game. If you need evidence both of that and of the importance of a smart, dedicated military, I’d recommend a recent depiction by Illia Ponomarenko of The Kyiv Independent of the brutal, terrifying fighting currently under way for Bakhmut. Courage and stamina are as important as they ever were. But bicep-flexing and bombast, not so much. In that case, however, what does determine military power? Obviously, I’m not a defence expert. But I do know something about applied maths – and contemporary wars are, to a large extent, about arithmetic....