Now we are arrived to the point when the combat has to end and liquidating a troop deployment comes in.
Combat deployment means an escalation of the situation, since previously the country they sent the troops was either a client maintained routinely or a client maintained by non-combat intervention.
Note: as a third case it can-be a non-client where the troops are, not discussed at the maintenance topic but the process of liquidation of the deployment is fairly the same.
US decision makers very easily ramp up the efforts and commit more money, troops, support when they see they don't make progress (eg Vietnam, Laos, Cambodia, Lebanon, Nicaragua, Afghanistan, Iraq), they have to arrive to the point where they decide they should stop. This point comes when the situation changes and they realize the it isn't at all how it looked like in the beginning. For example it started as a "life preserver" commitment, but it looks like an "open-ended combat" and they'd need a lot more troops but it might not be available for years. Or they are having an open-ended conflict which turns out to be a basket case, and have to set up a proxy force but it's impossible. They can escalate vertically from non-combat intervention to combat one, but they don't (can't) escalate horizontally from one combat intervention case to another.