I suggest we consider the art of war as it has evolved since Hiroshima. That bomb stunned the world because only two of them ended the biggest war of all time and for ever altered the way war would be waged. We ought to recognize that it also altered the reasons why war would be waged.
From 1945 to 1949 the United States had effective monopoly over atomic weapons but chose not to exercise them to go to war or even to threaten to go to war against Soviet bloc to liberate millions from enslavement. When Russia exploded a bomb in 1949 the entire landscape was immediately changed as radically as it had been in 1945. For one thing, the United States lost the unilateral ability to have its way-an option the left in America made sure we would never effectively exploit so long as we would have our way against a leftist nation.
Similarly, as the Cold War became entrenched the explosion of hydrogen bombs made the idea of war between nations which held nuclear weapons even more unthinkable. The advanced of Sputnik and success of intercontinental ballistic missiles capable of carrying nuclear warheads only made that reality more inescapable. So nuclear powers whether they are as strong as the Soviet Union with the capacity to destroy life in America or as weak as North Korea did not seriously contemplate war with each other (at least on our side), especially in the wake of the Cuban missile crisis.
But that left the acquisition of nuclear potential as a reason to go to war and that was precisely the reason invoked to justify the war in Iraq. The Israelis had already bombed the Iraqis and the Syrians in order to prevent them getting the bomb. Thus, the idea that making war to prevent the proliferation of atomic weapons had some currency at least.
So the United States waged war against Iraq to stop Iraq from getting atomic weapons and the intelligence was tragically faulty. Equally bad, the United States waged war against Iraq as you described, attempting to build a nation state rather than simply conquer. The result was tragic, the attempt was bungled, the American public fell away, Bush finally restored the matter with the surge, but Obama was elected and he forfeited whatever small victory might have emerged.
Meanwhile, the the Iranians have proceeded full throttle to develop the bomb which will make them as inviolate as North Korea and there simply is no stomach in America to make war to stop it. So the misguided war in Iraq, both in conception and execution, has resulted in the inevitability of Iran getting the bomb and incidentally in Iran getting great power in Iraq, the prevention of which was a secondary justification for the war. A loss all around on every count. Once Iran gets the bomb the entire balance of power in the Middle East will be swept away, America will become just one nuclear power among others as the region embarks on a race to arm themselves with atomic bombs. The chances of war and atomic war at that expand exponentially and the potential for economic mischief from the interdiction of the supply of oil to the world through the Straits of Hormuz will grow apace.
All of these unintended consequences emerged from faulty intelligence and faulty execution. Faulty intelligence perhaps came as a result of paranoia created by the very power of the bomb, perhaps as a result of retaining a Clinton appointed incompetent in the CIA in place. Faulty execution came about because we believed that we had rehabilitated Germany, Japan, South Korea and could do so in Iraq. We forgot we could not do so in Vietnam as you pointed out and we do not like to remember that the evolution of South Korea was not a uniformly pretty story. You are right, we forgot our lessons.
In the process we not only lost the war in Iraq, we lost allies in Europe, we lost any sense of fear of us in the Arab world, and we have contributed to our looming bankruptcy. We lost our self-confidence to the degree that we are unwilling to wage war when it is clearly in our national interest, specifically, we will not use military force to deprive Iran of bomb. So the war in Iraq served entirely the opposite result of its purpose in virtually every respect.
We should rethink why we wage war and how we wage war and stop agonizing over whether we can wage a moral war. War is horrible should be waged only as a last resort but when waged it cannot be successfully done fastidiously it must be done effectively which is a euphemism for being waged brutally - or not at all.
