Iran has thus far escaped military action in the post-9/11 world by dint of luck or guile or both, despite being situated between the two countries which suffered invasion by masses of American troops. Pro-war hawks have habitually planted stories about Iranian collusion of one sort or another with the insurgency in Iraq (the Iranians are probably more aligned with the actual Iraqi government). Now we’re seeing the same dynamic with respect to Afghanistan, and not from the pages of Commentary or some other neocon journal, but from the field commander himself.

The commander of NATO and U.S. forces in Afghanistan said Sunday there is “clear evidence” that some Taliban fighters have trained in Iran.

Gen. Stanley McChrystal told reporters in the Afghan capital that Iran — Afghanistan’s western neighbor — has generally assisted the Afghan government in fighting the insurgent group.

“There is, however, clear evidence of Iranian activity — in some cases providing weaponry and training to the Taliban — that is inappropriate,” he said. McChrystal said NATO forces are working to stop both the training and the weapons trafficking.

Here we go again. It bears mentioning that, in the late 1990s, Iran threatened all-out war with the Taliban. Members of the Revolutionary Guards Corps fought side-by-side with the Northern Alliance as they eventually overthrew the Taliban, and Iran backed the rebel group for years beforehand. During the US invasion after 9/11, Iran actually aided the United States in both providing intelligence and rebuilding the country, and they were instrumental in bringing the Northern Alliance on board with what eventually became the governing coalition in the country. Iran is Shiite; the Taliban are largely Wahhabist Sunni. None of this makes any sense.

But it’s not a new charge: David Petraeus said it in February 2009. Our foreign policy “consensus” seems to build lineups of super-villians and smash them together in league against the common enemy, whether they have evidence or not. It’s entirely possible that Iran recognizes that keeping US forces bogged down in Afghanistan takes pressure off of them, but that was basically the same argument made about Iraq, and the tales of Iran building or designing bombs for the insurgency never ended up with credible evidentiary support. The geopolitical dynamic cuts against such a thing happening with the Taliban even more, and yet Petraeus and McChrystal and the like keep insisting it. I’m sure you can draw a crooked line from some Iranian providing funding to someone who provided some equipment to someone and do a big six-degrees-of-separation game to connect them to the Taliban, but whether that constitutes material support is another story.

Even Petraeus and McChrystal don’t contend that this support is very deep or broad. But it’s always thrown out there, conveniently for Iran hawks who want to latch on to any pretext for military action anyway. McChrystal just handed them a gift, and the Obama Administration has yet to respond in a way that would cool down the rhetoric.