Some people have the idea that all wars are optional. Or at least a vast majority are for America. This especially includes Iraq.
Some wars are matters of survival. i.e. it is not always possible to choose your enemy. Sometimes the enemy chooses you.
It is possible to choose how to fight the enemy. Boots vs. bombs. However, boots can discriminate targets better than bombs can. They can also perform other useful tasks such as making friends and gathering intel. However, boots are limited by those in the military age range in any year. In the US we get about 1 million men entering that age range every year (which forms the main recruiting pool). The military gets about 10% of that pool every year. About the maximum possible in an all volunteer force. To increase the size of the force moderately rapidly (20,000 a year say), you would need to greatly increase retention rates. For that to be feasable you would need that many adequate performers who would like to be retained but are not due to Congressional force size limitations. Which I do not believe is the case.
Then you have the question of punitive expeditions vs transformative expeditions. One is quick, but often leaves a mess with the high likelyhood of having to cover the same ground repeatedly. Our you go in for a transformative expedition where your time horizon is much longer. All this affects troop man days spent in the field.
And lots of similar questions. Some political, some military, some economic, some cultural, some turning on social structure, some logistical, some technological, some related to infrastructure, etc., etc., etc.
All of this is complicated by the need to keep the oil flowing so civilization doesn’t collapse.
On top of that there is reaction. The enemy is always adjusting strategy, tactics, and war aims in response to our moves as we adjust same in response to his. And then there is the problem of keeping alliances together and disrupting enemy alliances.
Which is what makes the whole question a wicked problem. You can’t easily isolate the factors the way you can in a physics problem.
Cross Posted at Power and Control