U.S. President Barack Obama called Iranian President Hassan Rouhani last week in the first such conversation in the 34 years since the establishment of the Islamic Republic. The phone call followed tweets and public statements on both sides indicating a willingness to talk. Though far from an accommodation between the two countries, there are reasons to take this opening seriously -- not only because it is occurring at such a high level, but also because there is now a geopolitical logic to these moves. Many things could go wrong, and given that this is the Middle East, the odds of failure are high. But Iran is weak and the United States is avoiding conflict, and there are worse bases for a deal.

Iran's Surge

Though the Iranians are now in a weak strategic position, they had been on the offensive since 2003, when the United States invaded Iraq. They welcomed the invasion; Saddam Hussein had been a mortal enemy of Iran ever since the 1980-1989 Iran-Iraq War. The destruction of his regime was satisfying in itself, but it also opened the door to a dramatic shift in Iran's national security situation.

Iraq was Iran's primary threat after the collapse of the Soviet Union because it was the only direction from which an attack might come. A pro-Iranian or even neutral Iraq would guarantee Iranian national security. The American invasion created a power vacuum in Iraq that the U.S. Army could not fill. The Iranians anticipated this, supporting pro-Iranian elements among the Shia prior to 2003 and shaping them into significant militias after 2003. With the United States engaged in a war against Sunni insurgents, the Shia, already a majority, moved to fill the void.

The United States came to realize that it was threatened from two directions, and it found itself battling both Sunni insurgents and Shiite militias. The purpose of the surge in 2007 was to extricate itself from the war with the Sunnis and to block the Shia. It succeeded with the former to a great extent, but it was too late in the game for the latter. As the United States was withdrawing from Iraq, only the Shia (not all of them Iranian surrogates) could fill the political vacuum. Iran thus came to have nothing to fear from Iraq, and could even dominate it. This was a tremendous strategic victory for Iran, which had been defeated by Iraq in 1989.

After the Iranians made the most of having the United States, focused on the Sunnis, open the door for Iran to dominate Iraq, a more ambitious vision emerged in Tehran. With Iraq contained and the United States withdrawing from the region, Saudi Arabia emerged as Iran's major challenger. Tehran now had the pieces in place to challenge Riyadh.

Iran was allied with Syria and had a substantial pro-Iranian force in Lebanon -- namely, Hezbollah. The possibility emerged in the late 2000s of an Iranian sphere of influence extending from western Afghanistan's Shiite communities all the way to the Mediterranean. Former Iranian President Mahmoud Ahmadinejad had fairly realistic visions of Iranian power along Saudi Arabia's northern border, completely changing the balance of power in the region.

But while Syrian President Bashar al Assad was prepared to align himself with Iran, he initially had no interest in his country's becoming an Iranian satellite. In fact, he was concerned at the degree of power Iran was developing. The Arab Spring and the uprising against al Assad changed this equation. Before, Syria and Iran were relative equals. Now, al Assad desperately needed Iranian support. This strengthened Tehran's hand, since if Iran saved al Assad, he would emerge weakened and frightened, and Iranian influence would surge.

The Russians also liked the prospect of a strengthened Iran. First, they were fighting Sunnis in the northern Caucasus. They feared the strengthening of radical Sunnis anywhere, but particularly in the larger Sunni-dominated republics in Russia. Second, an Iranian sphere of influence not only would threaten Saudi Arabia, it also would compel the United States to re-engage in the region to protect Saudi Arabia and Israel. The Russians had enjoyed a relatively free hand since 2001 while the Americans remained obsessed with the Islamic world. Creating a strategic crisis for the United States thus suited Moscow's purposes. The Russians, buffered from Iran by the Caucasus states, were not frightened by the Iranians. They were therefore prepared to join Iran in supporting the al Assad regime.