Until now, most press coverage of the Benghazi matter has focused on the administration's misleading talking points explaining the attack on the U.S. facility in Libya. But just beneath the surface is the investigation into a potentially more explosive part of the Benghazi story: Whether the U.S. government did everything it could to save Americans whose lives were at risk in the chaotic hours of Sept. 11, 2012.

There were several hours between the first attack in Benghazi, which killed two Americans, including Ambassador Christopher Stevens, and a second attack, which left two more dead. Is there something the U.S. military could have done to rescue those last two and others who were badly wounded?

On Tuesday members of the House Armed Services Committee will question Pentagon officials in a classified session. The committee chairman, Republican Rep. Buck McKeon, R-Calif., last week told Defense Secretary Chuck Hagel that he remains "deeply concerned" about unanswered Benghazi questions. In a letter to Hagel, McKeon said he wants to know more about:

1. The account of events from the commander of the U.S. Site Security Team in Benghazi, including "the orders he received from higher authority;"

2. The presence of aircraft in the region, whether they were armed, how far they were from Benghazi, whether they would have needed in-flight refueling, and who in the military chain of command considered, or rejected, sending them to help;

3. The presence of unmanned aircraft in the region;

4. The status of a U.S. emergency team in Europe;

5. The presence of a Marine Corps Fleet Anti-Terrorism Security Team in the region;

6. What military preparations had been made to protect Americans in the area on the anniversary of the September 11, 2001 terrorist attacks.

Just to make sure he got a quick response, McKeon noted that he wants answers before he finishes work on next year's National Defense Authorization Act, which maps out funding for the Pentagon.

Meanwhile, some members of another House committee, the government reform panel, say getting answers out of the Defense Department has been a hard and often frustrating job. "The Department of Defense has helped create this fog, instead of candor, about [military] assets, where they were and when they were moving," says Rep. Jason Chaffetz, R-Utah, chairman of the national security subcommittee.

Chaffetz, like other members of his panel, was deeply struck by the recent testimony of career diplomat Gregory Hicks, who was the second-ranking State Department official in Libya after Ambassador Stevens. Hicks, who was in Tripoli the night of the attack, testified that he "wanted to send further reinforcements to Benghazi" and determined that a small team of special forces, led by a Lt. Col. Gibson, would go.

"The people in Benghazi had been fighting all night," Hicks testified. "They were tired. They were exhausted." And then the would-be relief mission came to a premature end before it began. "As Col. Gibson and his three personnel were getting in the cars," Hicks said, "he stopped, and he called them off and said -- told me that he had not been authorized to go."

Congress is still trying to learn who gave that order.

And then there are questions about what the commander in chief was doing while all that was under way. On "Fox News Sunday," White House adviser Dan Pfeiffer had little to say when asked what President Obama did as the attacks unfolded.

"He was in constant touch that night with his national security team and kept up to date with the events as they were happening," Pfeiffer said.

But with whom was he talking? asked host Chris Wallace. The president spoke once with the secretary of defense and once, hours later, with the secretary of state. What was he doing in between those talks?

"He was talking to his national security staff," Pfeiffer answered.

"Was he in the Situation Room?"

"He was kept up to date throughout the day."

It wasn't exactly an in-depth portrait of an engaged commander in chief. And it won't answer congressional questions about how involved the president was when his military commanders were deciding not to take action in Libya.

Lawmakers have heard testimony from higher-ups, including then-Defense Secretary Leon Panetta, saying there was nothing the U.S. military could have done to save the Americans in Benghazi. But congressional investigators realize that just as they need to hear from the man at the very top of the chain of command -- President Obama -- they need to hear from those down the chain to learn what really happened.

Byron York, The Washington Examiner's chief political correspondent, can be contacted at byork@washingtonexaminer.com. His column appears on Tuesday and Friday, and his stories and blogposts appear on washingtonexaminer.com.