In a stunning admission, Secretary of Defense Chuck Hagel, as well as the White House and Secretary of State John Kerry, announced today that the U.S. intelligence services have evidence that chemical weapons—including sarin nerve gas—have been used in the Syrian civil war. If true, that evidence would suggest that someone, most likely the Assad regime, has crossed President Obama's "red line" that would prompt the United States to finally intervene in the conflict.

White House laywers notified Senators Carl Levin and John McCain of the new information in a letter (which McCain posted on his website) that the intelligence community has physical evidence that the chemicals were used, but cannot fully confirm that they came from Assad's army. The letter does say that they will continue to investigate the matter to establish more proof. Hagel said the conclusion on the chemical weapons use was reached just within the last 24 hours. Just one day earlier, Hagel told reporters that "Suspicions are one thing. Evidence is another." It appears they now have the evidence.

Kerry also added that there have been two such chemical weapon attacks.

There have been indications for weeks that chemical weapons have been used in Syria, but so far the White House and Defense Department have been unwilling to say that the evidence was concrete. Earlier this week, Israeli intelligence said definitively that they had been used. The White House says more proof is needed to tie the weapon directly to Bashar al-Assad's forces, which Obama recently called a "game changer" on American involvement in the war. However, all indications are that they were used by his regime and they more weapons like it in their arsenal.

Hagel, who revealed the new Pentagon position while the United Arab Emirates on Thursday, told reporters that the use of chemical weapons "violates every convention of warfare." So the next question is: What is the U.S. going to do about it? The letter suggests that the U.S. will take the evidence they have to the United Nations, though what they will ask for beyond that is unclear. The Americans will almost certainly not act on their own, but they have may use this new development to finally join their allies who are calling for stronger intervention on behalf of the rebels.