Pentagon officials today confirmed that a “security team” of US forces came under attack from Ansar al-Sharia loyalists in the southern Yemeni city of Aden, but denied any injuries as a result of the attack. Ansar al-Sharia claimed one “CIA officer” killed in the exchange.

The difference in versions from the two sides actually misses the much more serious revelation of the report, that US ground troops are operating inside Yemen at all. There has certainly been no announcement to that effect, and indeed, several times the Obama Administration has “ruled out” sending ground troops to Yemen.

With pro-democracy protesters rallying against the US-backed dictator of Yemen virtually throughout 2011, Ansar al-Sharia seized the province of Abyan, and has made inroads in Aden, the former capital city of South Yemen. The US has repeatedly launched drone strikes against Ansar al-Sharia, claiming they are an “al-Qaeda front.”

But the drone strikes and the missile strikes and the assassination campaigns were always presented as an alternative to US boots on the ground, not a supplement to them. Talk of sending troops has always been followed up with denials that such a deployment was forthcoming, and what few “trainers” the Pentagon has previously admitted to having on the ground certainly wouldn’t be meandering through a major city just waiting to be ambushed. The administration has some serious explaining to do about how these troops came to be operating inside Yemen.