(CBS News) -- 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.
Some have complained the Obama Administration has not explained why there were no military resources available to turbulent North Africa on the Sept. 11 attacks, even at the large Souda Bay U.S. Naval base less than an hour's flight from Libya. The State Department's independent Accountability Review Board said government officials did everything they could, considering the challenges. The Defense Department has since reported implementation of improvements to make military resources more readily available if needed.
Another witness for Wednesday's hearing, Mark Thompson, is a counterterrorism expert. He's likely to address another sore spot surrounding the night of the attacks: the fact that the Obama Administration did not convene its top interagency counterterrorism resource, the Counterterrorism Security Group (CSG). According to Rep. Issa, Thompson will testify that he was locked out of the process "even though he was the individual who was supposed to react to these kinds of things."
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. Read more via CBS News...