Captioning sponsored by cbs this is the cbs evening news with scott pelley. Pelley good evening. You just heard the secretary of defense say it, u. S. Military forces are ready to go if and when the president gives the green light for a strike against syria. This would be punishment for that chemical weapons attack last week that left more than 300 syrian civilians dead, many of them women and children. Vice President Biden today became the highest Ranking Administration Official to declare that the assad regime was behind that attack. The Syrian Government denies it. U. N. Inspectors have not finished their investigation. So what evidence does the United States have . David martin has found out at the pentagon. Reporter before the u. S. Acts it plans to publicly reveal some of the intelligence which vice President Biden said today proves who is to blame for the mass casualties in syria. There is no doubt who is responsible for this heinous use of chemical weapons in syria, the syria r