The militant group Ansar al-Sunna posted a video on the Internet today purporting to show the explosion last week at a military mess tent in Mosul that killed 18 Americans and four others. The group, which earlier took credit for the attack, said its suicide bomber had spent a long time observing the camp and slipped inside during a change in the guards. The authenticity of the five-and-a-half-minute video – posted on a Web site that in the past has carried messages from insurgent groups – could not be determined. The Pentagon declined to comment early this afternoon, and officials from the military base in Mosul said they had not seen the video. Full Story