One further point about the “risk of retaliation.” Does any state that is attacked ever perceive that attack as retaliation for its own aggression? Israel perceives the Iranian nuclear program – which Iran protests is peaceful in intent – as an unequivocal provocation aimed at them. They point to Iran’s bellicose language and assertions that the Israeli state must be eradicated, to Iran’s actions in supporting Israel’s enemies in Lebanon and Gaza, and interpret Iran’s nuclear program in their light. From an Israeli perspective, a strike on Iran would be a defensive act – perhaps wise, perhaps unwise, but in either case a response to an Iranian provocation, and not an act of aggression.
Needless to say, Iran would perceive it as an unprovoked and blatantly illegal act of aggression, and might well respond, as it has threatened, with rocket attacks. But Israel would not perceive these attacks as justified retaliation against its aggression – it would perceive them as further evidence of Iran’s hostility.
If the United States came to Israel’s support in such circumstances, would most Americans perceive Iranian attacks on American soldiers or sailors, or on American interests abroad, to say nothing of American civilians, as “retaliation” for our “meddling” in a conflict between Iran and Israel? Isn’t it obvious that such attacks would only cause most Americans to line up behind even more forceful action against Iran?
I’m not saying that deterrence doesn’t work at all. But when it works, it works on decision-makers who fear both losing vital assets and failing to achieve their objectives. Pakistan can deter an Indian land invasion because Indian rationally wonders whether Pakistan might be willing to use nuclear weapons on Pakistani soil to annihilate the Indian army. This would make an Indian invasion futile; the only consequence would be the loss of a huge number of men and equipment. Similarly, the United States deterred a Soviet invasion of West Germany by promising to use nuclear weapons tactically to wipe out Soviet armor. The consequences of such a war for Germany and Poland would have been catastrophic – but the threat worked because the Soviets rationally understood that an invasion would be futile.
The fact is that there is no military in the world that can effectively deter American arms, because there is no military in the world that can impose those kinds of losses on us. Whether we can be deterred by a belated recognition of the profound limits to the efficacy of military power is an open question. The historical record doesn’t provide a lot of exemplars to follow in this regard, of hegemonic powers that retreated voluntarily because they realized that the promiscuous application of force was proving counterproductive, even in the absence of being dealt a decisive defeat. But, you know, we’re an exceptional nation, so hope springs eternal.