The United States is very good at using small forces to kill terrorists and dismantle their networks, but it is not very good at using large ones to manage other people's civil wars.Precisely. Punish bad people and groups as needed, eschew nation building.
The IS area is an ideal place to deploy the A-10 Warthog ground attack plane the Air Forces says it wants to dump. It is very resistant to ground fire and probably to shoulder-fired missiles as well.
The A-10 is just the ticket for getting in close and shooting up relatively low-tech troops with its 30 mm Gatling cannon and rockets. Imagine a Warthog with 23 tiny Toyota Hilux pickup trucks painted below the canopy. Brilliant.