A large literature is concerned with the consequences of war-related expenditures and how to finance them. Yet, there is little by way of understanding how expenditures affect the outcomes of wars, e.g., prevailing side, duration, or total destruction. I present a model of attrition in which I characterize the effects of resources on the outcomes of war for a military conclusion (when one side cannot fight anymore) and a political conclusion (when one side does not want to fight anymore). I discuss the role of GDP for both types of conclusions. I also analyze the mechanics of third-party support to a small country at war with a large one, e.g., Ukraine and Russia. Finally, I show that the model can fit actual battle data.