Peter Beinart compares:
The best precedent for all this is what Nixon did in the late Vietnam years. For roughly two decades, the U.S. had been trying to contain "communism" another ominous, elastic noun that encompassed a multitude of movements and regimes. But Vietnam proved that this was impossible: the U.S. didn't have the money or might to keep communist movements from taking power anywhere across the globe. So Nixon stopped treating all communists the same way. Just as Obama sees Iran as a potential partner because it shares a loathing of al-Qaeda, Nixon saw Communist China as a potential partner because it loathed the U.S.S.R.
Nixon didn't stop there. Even as he reached out to China, he also pursued détente with the Soviet Union. This double outreach to both Moscow and Beijing gave Nixon more leverage over each, since each communist superpower feared that the U.S. would favor the other, leaving it geopolitically isolated. On a smaller scale, that's what Obama is trying to do with Iran and Syria today. By reaching out to both regimes simultaneously, he's making each anxious that the U.S. will cut a deal with the other, leaving it out in the cold. It's too soon to know whether Obama's game of divide and conquer will work, but by narrowing the post-9/11 struggle, he's gained the diplomatic flexibility to play the U.S.'s adversaries against each other rather than unifying them against us.
(Hat tip: Weekly Standard)