Just one hour after the seven-hour-long terrorist attacks upon the US consulate in Benghazi began, our commander-in-chief, vice president, secretary of defense and their national security team gathered together in the Oval Office listening to phone calls from American defenders desperately under siege and watching real-time video of developments from a drone circling over the site. Yet they sent no military aid that might have intervened in time to save lives.

Why?

The attack began on September 11, at about 10:00pm Libyan time (4:00pm in Washington). Ambassador Chris Stevens and his small staff inside our consulate immediately contacted Washington and our embassy in Tripoli. Thirty minutes later, after the main consulate building was on fire and Ambassador Stevens was missing, Tripoli (400 miles away) dispatched an aircraft carrying 22 men. Much more formidable response resources including Special Operations Forces, transport aircraft and attack fighters were available 480 miles away at the US military base in Sigonella, Sicily, but were never dispatched. An F18 fighter jet blazing in with afterburner thundering to unnerve attackers and take out mortar locations could have reached Benghazi in an hour. Commandos could have arrived there within three hours. This was four hours into the seven- hour assault after President Obama, Vice President Biden and Secretary of Defense Panetta initially met at 5:00pm.

In the meantime, the terrorists forced the Americans to abandon the consulate with the ambassador still missing. They fell back to an annex building about a mile away. Looters ransacking the empty consulate discovered Ambassador Stevens lying unconscious from smoke inhalation on the floor and rushed him to a hospital where doctors were unsuccessful in saving his life. Not knowing who he was, they took a cell phone from his pocket and called numbers. By about 2:00am Libyan time, the American embassy received word he was dead.

At about that same time (four hours into the attack), the 22 men arriving at the Benghazi airport from Tripoli drove into the annex to assist the Americans trapped there. Around 4:00am enemy mortar rounds killed two defenders on the annex roof. The attack ended at dawn when Libyan militia finally arrived to aid our Americans.

CBS News has reported that a series of email alerts received late Tuesday evening provides additional information that was known by Obama administration officials shortly after the attack commenced. The messages were also independently obtained by ABC News. Although names of individual recipients were redacted, the source who requested anonymity said it appears they were sent to the State Department Operations Center to distribution lists and email accounts of top security officials at the State Department, Pentagon, the FBI, the White House Situation Room and the office of the Director of National Intelligence.

The first alert with a subject line “US Diplomatic Mission in Benghazi Under Attack” which arrived from Tripoli just 25 minutes after the attack began describes an assault on the compound by 20 armed people firing shots, with explosions heard as well. It reported that Ambassador Stevens and four COM (Chief of Mission) personnel were sequestered in the compound safe haven with the 17th of February militia providing security support. Another email arriving about one-half hour later reported that shooting had stopped and that the response team was attempting to locate COM personnel.

A third email received two hours after the attack commenced updated officials that Ansar al-Sharia, a terrorist group, claimed responsibility for the Benghazi attack on Facebook and Twitter, and had also threatened to attack the Tripoli embassy. The Facebook claim was subsequently denied by the group at a news conference in the following days, but not entirely convincingly, saying: “We are saluting our people for this zeal in protecting their region, to grant victory to the prophet. The response has to be firm.”

The Obama administration has an immediate obligation to inform the public why security responses were so tragically lacking both before and during the course of this terrible and fatal assault. Why was Ambassador Stevens, after he recognized and communicated the existence of a special 9/11 security threat, repeatedly denied protection he requested? It is clear that on August 2nd the consulate asked for an additional 11 security personnel to be added to the rotation of 24. Though the 11 were to replace temporary security staff, Stevens had made it clear that violence and terrorism were a threat amid a volatile political landscape. He wrote: “Due to the level of threat in regards to crime, political violence and terrorism, post feels this is an appropriate number of LES [locally employed staff] security personnel needed to further embassy diplomatic outreach missions. Violent security incidents continue to take place due to the lack of a coherent national Libyan security force and the strength of local militias and large numbers of armed groups.” He further emphasized that “Host national security support is lacking and cannot be depended on to provide a safe and secure environment.”

Andrew Wood, former head of a US military team in Libya, has reported, “...the security in Benghazi was a struggle and remained a struggle throughout my time there”. He added that the head of US security in the region had pushed for more people “...but was never able to attain the numbers he felt comfortable with.” Eric Nordstrom, the former security chief for US diplomats in Libya, has observed that he had been fighting a losing battle over numbers in which, “ ...we couldn’t even keep what we had.” He finally concluded after his contact with state department bosses that “...we were not going to get resources until the aftermath of an incident”.

And why, in the heat of battle with real-time communications regarding what was going on, didn’t our top leaders send responsive help that was so urgently needed? Past presidents have taken rapid actions to protect our people. For example, in 1984, President Reagan ordered US pilots to force an airliner carrying terrorists to land at Sigonella within a 90 minute window while they were still airborne. The Obama national security team had several hours to move forces from that same air base to Benghazi. We deserve an explanation.

This article was originally published at Forbes.com.

Larry Bell is a regular contributor to Forbes Magazine. He writes about climate, energy, environmental and space policy issues.