>Why didn't US intelligence realise what was coming and why wheren't proper precautions taken to disperse the troops so they wheren't on big fat target in a collapsible building.
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>That is a good question.
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>There was a committee that investigated afterwards and blamed it on a combination of security lapses, the barracks guards not carrying loaded weapons, and (probably biggest of all) a barrier that consisted of more than barbed wire (which has been replaced with other protective barriers). There may be more, I don't know all the details, but that's my understanding. Supposedly Iran issued warnings against the U.S. prior to the attack, because of our early financial support of Iraq in the Iran/Iraq war.

Prior to 9-11, it was common for guards to carry unloaded weapons. There was more concern over a fired weapon creating an international political incident than on true security at some locations. It was thought that the appearance of the weapons implied ammunition and would create a deterrence. That policy has since changed in most locations, but not all.