Throughout the night, sources say Americans on the ground in Libya at times felt helpless and abandoned.

“We relied on Washington for dispassionate assessment,” one eyewitness told CBS News. “Instead, they [Washington officials] were asking us what help we needed. We answered: ‘Send reinforcements!’ ”

But they were told immediate help wasn’t available.

Embassy personnel say they repeatedly asked the Defense Attache on site in Tripoli for military assistance.

“Isn’t there anything available?” one Embassy official says he asked. “But the answer was ‘no.’”

“What about Aviano?” the official pressed, referencing the NATO air base with US assets in northeastern Italy. “No,” was the answer.

Two of the four Americans killed that night died hours after the first attack began…

…Counterterrorism sources and internal emails reviewed by CBS News express frustration that key responders were ready to deploy, but were not called upon to help in the attack. National Security Council Spokesman Tommy Vietor told CBS News the CSG was not needed.