The ringleader is the U.S.-educated one-time chief of al-Qaida operations who bragged that he was responsible for the Sept. 11 terror attacks “from A to Z.” He was held for years in CIA detention, where agents waterboarded him 183 times.

The others include a one-legged militant, a self-described wannabe 9/11 hijacker, a money manager and the mastermind’s nephew, who has introduced himself in court as a Microsoft-certified software engineer.

All five are being brought to the Guantánamo war court Saturday to face arraignment as the architects of the worst terror attack on American soil in U.S. history.

And if that all sounds familiar, it is, because, yes, we’ve been here before.

The Pentagon is resetting the clock and restarting the Sept. 11 terror trial of Khalid Sheik Mohammed, 46, and four alleged accomplices, seeking to write the final chapter of the five men nearly a year to the day after Special Forces hunted down and killed Osama bin Laden.

These are the men whom President George W. Bush had brought to the U.S. Navy base in southeast Cuba for trials by military commissions in 2006, proceedings that President Barack Obama had halted to reform them with Congress in a bid to make them more credible in international law and human rights circles.

All five are accused of conspiring to organize, train or funnel funds to the 19 hijackers who flew four airliners into the World Trade Center, the Pentagon and a Pennsylvania field on Sept. 11, 2001. Each is charged with killing 2,976 people. Each faces execution, if convicted, by a method yet to be decided by Defense Secretary Leon Panetta or his successor.

And, if past court appearances are any indicator, Mohammed will take the lead defendant’s seat — and center stage — at the Guantánamo war court where he has described himself as a warrior for radical Islam and told a military judge that he welcomed martyrdom.

“We don’t care about the capital punishment,’’ Mohammed said at his last war court appearance in 2009. “We are doing jihad for the cause of God.”

Since arriving at Guantánamo, Mohammed has portrayed himself as a grandiose mystic — posing for a Red Cross photo kneeling on a prayer rug, flowing white robe and mammoth beard in one appearance, bragging to a military panel that he beheaded Wall Street Journal correspondent Daniel Pearl “with my blessed hand” in another, and calling himself a revolutionary just like George Washington.

He has signed his court documents as “KSM,” the nickname American law enforcement gave him in a worldwide manhunt.

In his war court charge sheet he comes off as a meticulous micromanager of the largest mass murder in American history — coaching the mostly Saudi hijackers on the most basic brutish English for their mission — “if anyone moves, I’ll kill you” — then having them practice the art of slaughter on sheep, goats and camels.

Nowhere does it mention that the CIA waterboarded him an unrivaled 183 times to break him at secret overseas prisons, using interrogation techniques the Obama administration now brands as torture. Nor does it note that he became so accustomed to the treatment that he counted off the seconds of near-drowning with his fingers, having realized that the CIA was not authorized to actually kill him.