The Iranian strategy has been to maintain ambiguity on the status of its program, while making it appear that the program is capable of sudden success -- without ever achieving that success. The Israeli strategy has been to appear constantly on the verge of attack without ever attacking and to use the United States as its reason for withholding attacks, along with the studied ambiguity of the Iranian program. The United States, for its part, has been content playing the role of holding Israel back from an attack that Israel doesn't seem to want to launch. The United States sees the crumbling of Iran's position in Syria as a major Iranian reversal and is content to see this play out alongside sanctions.
Underlying Israel's hesitancy about whether it will attack has been the question of whether it can pull off an attack. This is not a political question, but a military and technical one. Iran, after all, has been preparing for an attack on its nuclear facilities since their inception. Some scoff at Iranian preparations for attack. These are the same people who are most alarmed by supposed Iranian acumen in developing nuclear weapons. If a country can develop nuclear weapons, there is no reason it can't develop hardened and dispersed sites and create enough ambiguity to deprive Israeli and U.S. intelligence of confidence in their ability to determine what is where. I am reminded of the raid on Son Tay during the Vietnam War. The United States mounted an effort to rescue U.S. prisoners of war in North Vietnam only to discover that its intelligence on where the POWs were located was completely wrong. Any politician deciding whether to attack Iran would have Son Tay and a hundred other intelligence failures chasing around their brains, especially since a failed attack on Iran would be far worse than no attack.
Dispersed sites reduce Israel's ability to strike hard at a target and to acquire a battle damage assessment that would tell Israel three things: first, whether the target had been destroyed when it was buried under rock and concrete; second, whether the target contained what Israel thought it contained; and third, whether the strike had missed a backup site that replicated the one it destroyed. Assuming the Israelis figured out that another attack was needed, could their air force mount a second air campaign lasting days or weeks? They have a small air force and the distances involved are great.
Meanwhile, deploying special operations forces to so many targets so close to Tehran and so far from Iran's borders would be risky, to say the least. Some sort of exotic attack, for example one using nuclear weapons to generate electromagnetic pulses to paralyze the region, is conceivable -- but given the size of the Tel Aviv-Jerusalem-Haifa triangle, it is hard to imagine Israel wanting to set such a precedent. If the Israelis have managed to develop a new weapons technology unknown to anyone, all conventional analyses are off. But if the Israelis had an ultrasecret miracle weapon, postponing its use might compromise its secrecy. I suspect that if they had such a weapon, they would have used it by now.
