Clearly, suggesting that anyone aside from Assad gave the final order to launch a massive chemical weapons attack in the center of his own capital is tantamount to suggesting that Assad is no longer in charge of his regime—a suggestion for which there is no evidence. But the chain of military command inside Syria doesn’t end with the country’s president. The idea that Assad gave the order to carry out such a massive and politically dangerous attack without the approval of his Russian and Iranian advisers is also absurd—given the regime’s near-total reliance on Russian and Iranian strategic planning, supplies, fighters, and diplomatic backing for its week-to-week survival. Ditto for the idea that Russian or Iranian officers inside Syria gave their approval for such an attack without the blessing of the men at the top of their own chains of command: Ali Khamenei in Iran, and Vladimir Putin in Russia.

So, who—Khamenei or Putin—gave the OK? A reading of public statements by Iranian leaders suggests that they were at the least discomfited by the Syrian government’s actions, if not blind-sided by them. Both current Iranian President Hassan Rouhani and former Iranian President Rafsanjani condemned the attack, with Rafsanjani openly naming the Syrian government as the perpetrator. Rouhani, for his part, called on “the international community to use all its might to prevent the use of these weapons anywhere in the world, especially in Syria”—which hardly seem like the words of a man whose immediate boss just OKed the use of chemical weapons in Syria. Which leaves the more influential and powerful authority figure in the room by nearly every conceivable measure, including disposable wealth, diplomatic throw-weight, and advanced weapons systems: Vladimir Putin.

The most illuminating way of understanding why Putin would greenlight a nerve-gas attack that would cross America’s “red lines” in Syria is therefore to ask how the Russian president understands U.S. policy toward the proliferation of weapons of mass destruction—a policy whose real focus is not Syria but Iran.