ON SEPT. 11 and for days afterward, U.S. embassies in Cairo and in many other Muslim capitals were besieged by demonstrators protesting an anti-Muslim video they believed was a U.S. product. President Obama and the State Department were right to respond to those protests by condemning the video as well as the violence, and by defending free speech rights, as Mr. Obama did in an address to the United Nations.

We now know, however, that an attack on two U.S. installations in Benghazi, Libya, on the night of Sept. 11, which killed ambassador J. Christopher Stevens and three other Americans, was not related to those protests. Instead, it was an organized terrorist attack by scores of heavily armed militants who overwhelmed five U.S. diplomatic security agents, a rapid-response force, and two or three members of a Libyan militia. Though the assault was probably staged by a local extremist group, U.S. officials now believe that the North African chapter of al-Qaeda may have been involved in its planning.

The coincidence of these events led to some confused assessments and even more confused rhetoric by the Obama administration, which initially described the Libya attacks as growing out of a protest of the video. President Obama, who has been boasting on the campaign trail that “al-Qaeda is on its heels,” was particularly slow to publicly recognize what happened; asked on Sept. 25 whether a terrorist attack had taken place, he responded that “we are still doing an investigation” — even though Secretary of State Hillary Clinton had labeled it terrorism four days earlier.

Republican claims that the administration has engaged in a deliberate coverup of what happened on Sept. 11 are nevertheless overblown. In a House hearing Wednesday, GOP representatives offered no evidence that their favorite target, U.N. Ambassador Susan Rice, deliberately hid the truth on Sept. 16, when she described the attack in television interviews as the outgrowth of a protest against the video. On the contrary, testimony by Undersecretary of State Patrick F. Kennedy, who said Ms. Rice’s account was based on reporting by the intelligence community, was credible.

At the same time, GOP House investigators have helped make clear that the Benghazi attack should have come as no surprise to the U.S. mission — and that it was preceded by terrible decisions about security. Though extremist militants were known to be operating in the Benghazi area, only a tiny force protected the U.S. compound; the State Department denied a request by the regional security officer to extend the term of a 16-member military squad that had been protecting the embassy in Tripoli. An assertion at the hearing by Deputy Assistant Secretary of State Charlene Lamb that “we had the correct number of assets in Benghazi at the time of 9/11” was patently absurd; the White House quickly repudiated it.

In an interview with ABC News on Wednesday, Mr. Obama acknowledged that “the information may not have always been right the first time.” He added that “the “bottom line is . . . I want us to get the folks who did it, and I want us to figure out what are the lessons learned.” That’s the right focus — and it’s what Congress should hold the administration accountable for.