Military Orders -- To Obey or Not to Obey?

The Army has announced they are investigating up to 19 members of a platoon from the 343rd Quartermaster Company (currently deployed to Iraq) for refusing to deliver supplies, as they felt the mission was "too dangerous."

Do military members have the right to disobey orders because they feel the mission is too hazardous?. Of course not. However, in some cases, military members not only should, but are required to disobey a direct order.