The United States has an extraordinary ability to defeat any conventional armed force on the planet; our tanks, ships and planes will make short work of any enemy in frontal war. For that very reason, the enemies we face will not confront us in suicidal direct conflict; instead, they will fight us indirectly, as insurgents and terrorists. Waging war against us from amid the sea of innocent populations handcuffs our conventional strength and dooms us to fight grinding forever wars like those in Iraq and Afghanistan.
It's far better to have our friends and allies fight our terrorist and insurgent enemies than to do it ourselves. They have the local knowledge of human and geographic terrain, speak the language and understand the culture. But to fight effectively, foreign forces need American support, especially communications, intelligence and airpower. Without it, they will be less effective than they should be, and may even crumble under contact, as the Iraqi Armed Forces we spent billions of dollars training and equipping did recently.
Our response to that disaster was to deploy a small force of advisers — sadly, too little, too late. It would have been far better to have left advisers with the Iraqi Army when our own combat forces departed. Properly trained in Arabic and in the skills of combat advising, they could have prevented the return of Islamist murderers to a country too many of my friends died in, wresting control from insurgents just a decade ago.