An army can live off the land in most places, although deserts are an obvious exception. What can’t be found, stolen or made on the march, however, must be carried with it: arrows, spears, spare armour and weapons by the ox-cart load, medical supplies, decent wine from home, and the hundred other little things that make campaigning bearable as opposed to just plain miserable. Logistics, the art of collecting all these supplies together and keeping them moving with the army, wins battles more reliably than military genius. Knowing where to march is the province of the strategist; getting everyone and everything there in time is logistics. Good generals know that supplies win wars. It is pointless taking a soldier to a battlefield if he is hungry, thirsty, ill or exhausted. He will not give his best in such circumstances, no matter how inspiring the leadership qualities of his commanders.