The select Benghazi Committee holds its first open hearing Wednesday, employing broad congressional powers to try to answer lingering questions ranging from what led to the fatal 2012 terror strikes on a U.S. outpost in Libya to what is being done to better protect U.S. diplomats worldwide.

The hearing by the Republican-led House committee will focus on the extent to which the State Department has implemented post–attack recommendations made by the Accountability Review Board.

The department created the five-member, independent board just weeks after the Sept. 11, 2012, attacks in which four Americans -- Ambassador Chris Stevens, information specialist Sean Smith and Navy SEALs Tyrone Woods and Glen Doherty -- were killed.

“There are still facts to learn about Benghazi and information that needs to be explained in greater detail to the American people,” Rep. Trey Gowdy, R-S.C., the committee chairman and a former federal prosecutor, said earlier this month. “And this committee will do just that.”

In a December 2012 report, the board issued 29 recommendations to fix what it called “systemic” leadership and senior management failures that led to the “grossly” inadequate security at the U.S. outpost.

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Congressional Republicans were immediately critical of the report and its authors, saying they downplayed key decisions by top department officials, instead putting too much blame on their subordinates.

Scheduled to testify Wednesday are Greg Starr, the department’s assistant secretary for Diplomatic Security, and Mark Sullivan and Todd Keil, members of the Independent Panel on Best Practices, created to review the accountability board’s efforts.

Sullivan is the panel chairman and a former Secret Service director. Keil is a former Department of Homeland Security assistant secretary.

The board was led by Ambassador Thomas Pickering and Adm. Michael Mullin, who have already testified before Congress and are expected to be called before the select committee.

The fatal attacks, which the White House said in the immediate aftermath were sparked by an anti-Islamic video, have been the subject of roughly 12 congressional hearings.

However, the House created the select committee in May 2014 with the expectation that its subpoena powers and other tools would bring forth new witnesses and resolve unanswered questions.

The committee is expected to address several other key issues, including to what extend the U.S. attempted to stop the attacks and rescue U.S. personnel and whether the White House response, weeks before voters decided whether to re-elect President Obama, was politically motivated.

U.S. Special Forces captured and arrested Libyan Ahmed Abu Khattala in June in connection with the attacks on the two U.S. facilities, and he is awaiting trial in the United States.

The committee’s 12 members -- seven Republicans and five Democrats -- have been working since being appointed by hiring staff, gathering information and meeting with family members of the four men killed.

House Democrats were reluctant at first to join the committee.

They argued the issue has been full investigated and that further efforts are just politically-motivated attempts to keep Benghazi in Americans’ minds through the 2014 midterms and the 2016 presidential elections, in which Hillary Clinton, secretary of state at the time of the attacks, is the presumptive Democratic front-runner.

“I do not believe a select committee is called for after eight reports, dozens of witness interviews and a review of more than 25,000 pages of documents,” Maryland Rep. Elijah Cummings, the top Democrat on the select committee, said this spring. But “I believe we need someone in that room to defend the truth.”