An independent team reviewing the Sept. 11 terrorist assault on the U.S. consulate in Benghazi, Libya has pinpointed the root cause of the events that left four Americans, including Ambassador J. Christopher Stevens, dead.

Call it incompetence. More specifically, call it reckless disregard — particularly in Washington — for the emerging dangers in eastern Libya and lax security on the scene.

"Systemic failures and leadership and management deficiencies at senior levels within two bureaus .<TH>.<TH>. resulted in a Special Mission security posture that was inadequate for Benghazi and grossly inadequate to deal with the attack that took place," the report concluded.

The two State Department bureaus faulted for failing to coordinate and plan for adequate security were Diplomatic Security and Near Eastern Affairs.

The 39-page report confirms some facts that have already been established, including that, despite initial reports, there was no public protest preceding the assault on the diplomatic mission and a CIA annex. This was a coordinated attack by armed terrorists who overpowered the compound's four Libyan guards apparently without much resistance.

"The four (Libyan guards) assigned .<TH>.<TH>. were insufficient and did not have the requisite skills and reliability to provide a reasonable level of security on a 24/7 basis for an eight-acre compound with an extended perimeter wall," the report concluded.

While the report offers a scathing analysis of security lapses surrounding Stevens and his mission in Libya, but it leaves other questions unanswered. For example, State Department officials have testified, and the report confirms, that there was no specific threat of an attack leading up to the 9/11 assault. But why wasn't the growing evidence of a general threat against diplomats in the region enough of a reason to elevate security?

The report lists a series of attacks in the spring and summer that showed a growing risk. These included an IED explosion that left a large hole in the compound's exterior wall on June 6 and the launching of rocket-propelled grenades at the British ambassador's convoy five days later, an attack that left two security officials injured. The United Kingdom shut down its mission in Benghazi the following day.

The team blamed unnamed State Department officials in Washington for ignoring requests from the U.S. Embassy in Tripoli for more guards and safety upgrades to the mission in Benghazi. Furthermore, the investigation team found "a pervasive realization among personnel who served in Benghazi that the special mission was not a high priority for Washington when it came to security-related requests, especially those relating to staffing." Three senior State Department officials in charge of diplomatic security resigned Wednesday. Did responsibility end there?

William Burns and Thomas Nides, both deputy secretaries of state, are scheduled to testify today before the Senate Foreign Relations Committee and the House Foreign Affairs Committee. Committee members need to press for answers.

Whether the reasons for inadequate security were the result of shortages in budget or lapses in judgment, the public deserves to know. Moreover, the families of Stevens and the others killed deserve to know — as do the families of those still serving in the 273 U.S. diplomatic missions around the world.