Stephen Hadley unintentionally explains the futility of arming the Syrian opposition while calling for the U.S. to do just that:

The longer this struggle goes on, the more militarized it will become. The more militarized it becomes, the more Syria’s future will be dictated by who has the most guns, not who gets the most votes.

At no point does Hadley describe how arming Syrian rebels is connected to any of his other recommendations, nor does he explain how providing arms to the far weaker side in a civil war will lead to the desired outcome of toppling the government. If Syria’s future will be dictated by “who has the most guns,” it is difficult to see how contributing to the militarization of the uprising will prevent the eventual victory by the much better-armed side. He does not specify which armed groups inside Syria he wants to arm, and he does not tell us how the armed opposition would be put under the control of the Syrian National Council that he wants the U.S. to support. He doesn’t address any of the most important objections to this course of action. The call for arming Syrian rebels seems formulaic and unrelated to anything else he says.

Wouldn’t funneling arms to the opposition undermine the appeals he wants to make to current regime supports and/or fence-sitters? How does it make it more likely for loyalist officers to abandon Assad by fueling a Western-backed insurgency directed against them? If the SNC is not in control of armed opposition groups inside Syria (and it still isn’t despite the recent formation of the SNC’s “military bureau”), why should loyalist army officers and minority groups support the SNC? Is the SNC in any position to fulfill the guarantees of security that Hadley wants to offer to these groups as incentives to switch sides? What reason do any of these groups have to trust the assurances that Hadley wants the U.S. and others to provide, and why should they expect these assurances to be honored? In principle, it makes sense to “motivate the key pillars of the regime to split away” when the goal is overthrowing the regime, but I don’t see anyone offering the “key pillars” a compelling reason to take enormous risks in exchange for some extremely convenient promises and optimistic scenarios.

Hadley’s conclusion is hard to take seriously:

The United States will need to take the lead so that such arming does not become a vehicle for a proxy war in Syria between competing regional states but instead contributes to building a stable and democratic Syria for all its people.

Arming rebels in a civil war against a regime that is backed by other states is a proxy war between competing regional states. If the U.S. “takes the lead” in doing this, that will simply put the U.S. at the head of one of the coalitions of states competing for influence via Syrian proxies.