A few recent articles have been providing great summaries of the complexities of the Iranian situation. First up, Newsweek examines what it calls America’s Hidden War with Iran. Going all the way back to 9/11, Michael Hirsh reminds that

For Iran’s reformists, 9/11 was a blessing in disguise. Previous attempts to reach out to America had been stymied by conservative mullahs. But the fear that an enraged superpower would blindly lash out focused minds in Tehran. Mohammad Hossein Adeli was one of only two deputies on duty at the Foreign Ministry when the attacks took place, late on a sweltering summer afternoon. He immediately began contacting top officials, insisting that Iran respond quickly. “We wanted to truly condemn the attacks but we also wished to offer an olive branch to the United States, showing we were interested in peace,” says Adeli. To his relief, Iran’s top official, Ayatollah Ali Khameini, quickly agreed. “The Supreme Leader was deeply suspicious of the American government,” says a Khameini aide whose position does not allow him to be named. “But [he] was repulsed by these terrorist acts and was truly sad about the loss of the civilian lives in America.” For two weeks worshipers at Friday prayers even stopped chanting “Death to America.”

All this at a time when there were crowds in other Muslim nations celebrating the 9/11 attacks. I mean, it almost sounds like a regime ripe to be co-opted for our struggle against a global Salafi insurgency!
Hirsh goes on to summarize the pivotal role Iran played in stablizing post-war Afghanistan. Even after President Bush’s inclusion of Iran in the “Axis of Evil” during the 2002 SOTUS, Iran was looking to deal with the US.

After U.S. tanks thundered into Baghdad… “We had the strong hand at that point,” recalls Colin Powell, who was secretary of State at the time. If anything, though, America’s lightning campaign made the Iranians even more eager to deal. Low-level meetings between the two sides had continued even after the Axis of Evil speech. At one of them that spring, Zarif raised the question of the Mujahedin-e Khalq (MEK), a rabidly anti-Iranian militant group based in Iraq. Iran had detained a number of senior Qaeda operatives after 9/11. Zarif floated the possibility of “reciprocity”—your terrorists for ours.
…Around this time what struck some in the U.S. government as an even more dramatic offer arrived in Washington—a faxed two-page proposal for comprehensive bilateral talks. To the NSC’s Mann, among others, the Iranians seemed willing to discuss, at least, cracking down on Hizbullah and Hamas (or turning them into peaceful political organizations) and “full transparency” on Iran’s nuclear program. In return, the Iranian “aims” in the document called for a “halt in U.S. hostile behavior and rectification of the status of Iran in the U.S. and abolishing sanctions,” as well as pursuit of the MEK.

This was the time for making a deal with Iran. Strategy is all about knowing when to stop destabilizing and start consolidating one’s gains. Immediately in the aftermath of a successful invasion, not yet engaged in a vicious COIN effort, and looking to maintain momentum - this was the strongest America’s hand would be. Tragically, this was also the hardest time for our administration to think about making a strategic deal with Iran, flush as it was from the successful toppling of Saddam.

Complicating the situation was a difficulty US negotiators had always faced when it came to Iran: “determining who in the byzantine regime to talk to, and whether they could deliver anything.”

Iran’s power waxed after Ahmadinejad took office, peaking last summer during Hezbollah’s campaign against Israel, while America’s hand grew weaker and weaker. The past few months have witness a moderate reversal in these trends.

The real thrust of Washington’s multipronged attack is political. Banking restrictions levied by the U.S. Treasury have begun to pinch the Iranian economy. Voters angry about rising prices dealt Ahmadinejad an embarrassing blow in municipal elections in December, when his supporters were trounced. That wouldn’t much matter if he still retained Khameini’s support. But that may no longer be the case. The Khameini aide says the Supreme Leader blames Ahmadinejad’s overheated rhetoric about Israel and the Holocaust for the unanimous Security Council resolution that passed in late December, demanding that Tehran suspend its nuclear program.

In addition to these diplomatic and economic pressures, the US and Israeli have stepped up covert action by intelligence assets. These covert actions may include assassinations of Iranian nuclear scientists by Mossad.

While the US and Iran have experienced periods of advantage over the other, each has overplayed its hand during its periods of dominance. This current moment, therefore, has opportunities and dangers. Opportunities due to the Bush administration’s need for Iranian cooperation in stabilizing Iraq, combined with a waning of Iranian power from its peak last summer. Danger due to the multitude of friction points that could - intentionally or inadvertantly - draw Iran, Israel and the US into direct combat.