Strategy and tactics would be the logical answer, of course. The answer is logistics. A war cannot be fought without ammunition, replacement weapons, and subsistence for the armed forces.
History reveals the truth about the dominant nature of logistics.
Supporting a Standing Army Louis XIV of France was one leader who learned the hard facts about the effects of logistics on war. When Louis became king in 1643, he inherited a united kingdom that was generally well financed. However, to field the type of army he would need to make France a great power and bring himself personal glory, Louis needed far more money. At that time, large armies were rarely fielded because of their great expense. France was one of the first nations to develop a modern industrial system that could supply the money needed to purchase and transport the sinews of war.