Robinson is on his island. He's good at collecting coconuts and a poor fisherman, but he would like to eat fish much more than coconuts. Friday appears on the scene. Friday is a better fisherman, but prefers coconuts over fish.
Welcome to microeconomics 101, the simplest model of trade and how trade between two agents is a win-win for both and actual improves aggregate output. There are diagrams for this, of course. Macroeconomics has its analogy in free trade theory.
Economics is about how cooperation can lead to a better aggregate and individual outcome.
Military theory is the evil twin: It's not about how to achieve what cooperation, but about how to force others into compliance. Its only efficiency goal is to force the own will on others at least expense, whereas the aggregate outcome and at least one party's individual outcome (usually everyone's) are worse as a consequence of the process of (trying to) forcing one's will on others.
Economics good, military theory evil.
Too bad; countries often need the latter for avoiding its worst consequences, even if they don't like it.
Yesterday I did refer to economists' appraisal of biology as a supporting science, and suggested that military theory and political science could do the same. This wasn't by accident. Military theory and economics may be opposites, but this makes them similar as well. Economic theory is about cooperation, military theory is about confrontation. Both are about an interaction of agents, whereas a great many sciences such as geology, physics and math aren't about the interaction of thinking and competing humans at all.
Political science is in between both, in that it is both about cooperation and confrontation between competing agents (in military theory you usually don't compete with allies unless some honour code is in effect or said allies are expected to become rivals or enemies soon thereafter).
The similarities are promising enough; one field may gain insights by paying attention to other fields' findings. There sure is a better match than the faux analogies of geometry (Renaissance military thinkers) or misunderstood physics (von Clausewitz).