I've been captivated by the uprising in Iran, but not terribly optimistic about its outcome. For a revolution to succeed, it generally needs one of two things to happen: Either it needs its own weapons, or it needs mass defections by the state security forces. There's no evidence that the first could happen. But some scattered evidence of this is starting to appear. Nico Pitney (who has been writing a must-read blog on Iran) writes, "From an Iranian on Twitter: "CONFIRMED by ONE source, police wearing green scarves."

Meanwhile Robert Fisk reports:

It was interesting that the special forces - who normally take the side of Ahmadinejad's Basij militia - were there with clubs and sticks in their camouflage trousers and their purity white shirts and on this occasion the Iranian military kept them away from Mousavi's men and women.

In fact at one point, Mousavi's supporters were shouting 'thank you, thank you' to the soldiers.

One woman went up to the special forces men, who normally are very brutal with Mr. Mousavi's supporters, and said 'can you protect us from the Basij?' He said 'with God's help'.

It was quite extraordinary because it looked as if the military authorities in Tehran have either taken a decision not to go on supporting the very brutal militia - which is always associated with the presidency here - or individual soldiers have made up their own mind that they're tired of being associated with the kind of brutality that left seven dead yesterday - buried, by the way secretly by the police - and indeed the seven or eight students who were killed on the university campus 24 hours earlier.

It's going to take a lot more of this for the revolution to succeed, but this is the kind of thing to look out for.

--Jonathan Chait