This may prove to be the darkest week in Iran's recent history. There is, it seems, nowhere to go. Yet the nature of this darkness, its awkward fit with the official meaning of the Islamic regime, may show us a way forward.
Exactly a year ago Sunday, when it became apparent that Mahmoud Ahmadinejad had claimed victory in an election whose results and conditions were not at all clear, the streets of Tehran began to fill with people.
It does not really matter whether Mr. Ahmadinejad stole an election that went against him (as protesters claim) or not; what this year of protest has shown is that Iran is far more fissiparous than anyone had thought, and that only force and fear, not faith and support, keeps it conglomerated. Even if you discount the hyperbole the foreign media directed at the "green tide" last year, this was by far the largest and lengthiest uprising in the Iranian revolution's history.
It encompassed a huge swath of society; most significantly, it involved large numbers of clerics and top leaders, including former prime ministers, who were actively involved in the 1979 revolution and whose loyalty to the state is beyond question: This could not easily be dismissed as the work of radical guerrilla groups or outside agitators salaried by the United States or Britain.
As the year has progressed, and especially after the authorities went on a killing spree in December, on the holy day of Ashura, these figures have become more antipathetic toward the regime itself: There is now an official, built-in resistance with a name and an identity.
But you will probably not be seeing much of this resistance this week. It has become far, far too dangerous. Thursday, the key leaders of the protests, former prime minister Mir Hossein Mousavi and Mehdi Karroubi, told people to stay home: The alternative was a slaughter. The regime's shift from authoritarian to totalitarian - its adoption of Stasi-like practices that had not been part of its repertoire before - have rendered such demonstrations temporarily impossible.
There have been, officially, more than 5,000 protesters arrested and imprisoned, a shocking number of them tortured, raped, humiliated or flogged. Hundreds of protesters, dissidents and writers have been killed in gruesome public executions (338 last year and 115 so far this year, with 38 more "political prisoners" currently sentenced to death) and scores (officially 36 but probably more than 100) killed at protests or dying in prison.
So there is silence. But there is another source of darkness, one that has overtaken the headlines. Thursday, the United Nations Security Council voted in another set of sanctions, intended to "isolate" Iran further in an effort to get Mr. Ahmadinejad to bring his nuclear program under the strictures of the UN Nuclear Non-Proliferation Treaty.
Some, looking at the quashing of dissent and therefore the diminishing possibility of regime change, think this means hard options are the only ones worth considering, even though a nuclear weapon is years away even if Iran is considering one, which seems probable.
But look more closely at those fissures. This week, I spoke with Maziar Bahari, the Iranian-Canadian journalist who spent months being tortured in Tehran's Evin Prison last year. He pointed out that the regime is trying hard to adopt East German-style totalitarianism, but is doomed to fail because it is so divided against itself - the prison itself contains three wings, each controlled by a different security service loyal to a different branch of government.
Even the Revolutionary Guard, which controls much of the economy, is far from a stable entity. In a new documentary that interviews officers who recently defected to Turkey, they speak of growing factionalism.
One former guard describes how Mr. Ahmadinejad's officials were able to crack down on last year's protests only by packing the guard with young, poor recruits from rural villages (an extremely rare group today); the more experienced members would not shoot.
An attack on Iran would consolidate the population against the attackers and behind Mr. Ahmadinejad. Sanctions themselves, though, could have an important effect. My research there found that ordinary Iranians blamed the last round of sanctions on Mr. Ahmadinejad: His international bumbling (and Iranians do see it that way) brought hardship. These new sanctions, combined with the shame of this very visible necessity for repression, could have an important effect come the next election, which will occur well before any nuclear weapon could be built. And remember, the current protest leaders tried very hard in 2003, when they were in power, to abandon the nuclear program for an alliance with the West, until George W. Bush rebuffed him.
Three years ago, when Mr. Ahmadinejad's crackdown on dissent was just a year old, I spent an afternoon in Tehran with the great philosopher Dariush Shayegan. Before, he said, the regime stayed aloft because most people believed in it. But now, "I think the Iranians have understood something - that the theocratic system does not work. They have realized that religion is just a vehicle for power, that's all. It's become an instrumentalization of Islam, a Bolshevization of the regime." When fissures like that open up, things will eventually cleave apart from within.