From chicagotribune.com.

Barack Obama and Mitt Romney are agreed on one thing: If Iran refuses to give up its apparent pursuit of nuclear weapons, at some point we will have no choice but to intervene with military force. The discussion, to the extent there has been one, is just about where that point lies. But an attack on Iran would not be the end of matter. It would just be the start.

So says retired Marine Corps Gen. Anthony Zinni, who stopped by the Tribune last week to talk about what might happen after U.S. and/or Israeli planes carry out a preemptive attack on Iranian nuclear sites. The question he wants to ask those in charge, he says, is: “Do you understand what you’re getting into?” As head of Central Command, which covers the Middle East, he gave questions of that kind a lot of thought.

An American president might have in mind a brief campaign that would cripple the Iranians. But the Iranians have the option to strike back in all sorts of ways. “What if they lob a missile into Fifth Fleet headquarters?” he asks. “Or we have another 9/11?” He advises, “Don’t think it’s necessarily limited.”

Zinni notes that Iran has mobile missiles — which it could use to hit Israel, Europe or U.S. bases in the region. It could send suicide boats to fire cruise missiles at our Navy ships. They could lay mines in the Persian Gulf, which would disrupt shipping and send oil prices through the roof.

If Iran escalates, he says, the president needs to know he will respond. In an expanded war, we might find ourselves forced to try to bring down the Iranian regime. For that, ground forces may be unavoidable. Can he envision using 100,000 troops to march on Tehran? “You’d have to plan for it,” he warns — not assume it will happen, but be ready for the possibility.