AP Photo

Back in 2001, as the United States worked with other world powers to reassemble the pieces in Afghanistan, Iran was a key ally. Despite its long-running conflict with the United States, Tehran pressured and cajoled its allies in the anti-Taliban Northern Alliance to compromise in support of what is now the Hamid Karzai-led government in Kabul.

Since then, however, Iran has hedged its bets, providing overt support to Karzai’s government – including, at one time, literally bags of cash – while, at the same time, quietly giving covert backing to the various Afghan insurgent groups including the Taliban. Now there are new reports that Iran may be setting the stage for a more lethal form of aid to the Taliban, sending a not-so-subtle message to Washington that...