Gentlemen, let's consider a few things:

1. The people of Lebanon rose against their government, and their government resigned.

Let's assume Syria moves its troops back in to regain control.

2. In the last state of the union speech, Bush said that he will help any people revolting against their government.

3. Due to past experiences with Bush, we know he usually keeps his word on international policies.

4. By implication, the U.S. should interfere if Syria attempts to regain control.

5. Iran and Syria signed a pact to help each other against aggressors.

6. If the U.S. interferes with Syria in Lebanon, then Syria and Iran will fight against the U.S.

... There is a possibility of a very large war on the horizon.

A reaasonable step by step logical progression...
BUT
Syria cant act openly to exert control millitarily here or the world community WILL condem them....that would make it difficult for Iran to stand by Syria unless there was a unilateral action from the USA.

There is also the possibillity that the spoken alliegance by iran twords syria is nothing more than hot air rhetoric...and as such is only sabre rattling.

I feel both Iran and Syria would be really jeapordizing what little standing they have in the world if they openly attempt to interfere in lebanon...
getting caught supporting terrorism or instabillity in the mid east would not go over well with the world community.