Saturday marked 20 years since the Sept. 11, 2001, terror attacks shocked the world – and the Taliban control Afghanistan for the first time in just as long.

Khalid Sheikh Mohammed, the alleged al Qaeda mastermind behind the attacks, and four other accomplices detained at Guantanamo Bay appeared in court for the first time in over a year last week for pretrial hearings following coronavirus delays. 

The group faces thousands of charges for murder, terrorism, and hijacking in connection with the Sept. 11 plot, which killed 2,977 innocent people. More than 2,000 first responders have since died due to 9/11-related illnesses. Tens of thousands of survivors and responders were exposed to hazardous debris.

This March 2003 photo obtained by The Associated Press shows Khalid Shaikh Mohammad, the alleged Sept. 11 mastermind, shortly after his capture during a raid in Pakistan.  (AP)

The ensuing war in Afghanistan also claimed the lives of 2,325 U.S. service members, impacting exponentially more people back home.

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"The 9/11 attacks have so much ripple tragedy inherited through a generation now to follow the families that survived," said Asra Nomani, an author, activist, and former Wall Street Journal reporter. "And we have to remember that justice still has to be served."

The attacks and two decades of war have scarred generations, she said, with children losing parents and parents losing children.

Al Qaeda leader Usama bin Laden was killed by U.S. Navy SEALs on May 1, 2011, but the terror attacks’ alleged mastermind has yet to go to trial – even though the U.S. has had him in custody for more than 15 years.

When Mohammed and his alleged accomplices entered a pretrial hearing Tuesday, their first court appearance in more than 500 days, they were seen smiling.

The quintet have been held at Guantanamo Bay since September 2006 after several years in clandestine CIA detention facilities following their capture.

Mohammed has also taken responsibility for killing Wall Street Journal reporter Daniel Pearl, the man abducted five months after 9/11 while investigating the potential ties between the "shoe bomber" Richard Reid and a Pakistani cleric. 

FILE - In this April 15, 2007, file photo, Dr. Judea Pearl, father of American journalist Daniel Pearl, who was killed by terrorists in 2002, speaks in Miami Beach, Fla. Pakistan's Supreme Court on Thursday, Jan. 28, 2021, ordered the release of Ahmad Saeed Omar Sheikh who was convicted and later acquitted in the gruesome beheading of American journalist Pearl in 2002. The court also dismissed an appeal of Sheikh's acquittal by Pearl's family. (AP Photo/Wilfredo Lee, File)

In the December after 9/11, Reid, another al Qaeda member, attempted but failed to detonate explosives in his shoes on an American Airlines flight from Paris to Miami. 

Nomani is a friend of Pearl’s. She let him stay at her rental home in Pakistan while he covered the case. In the 20 years since, she said he’s been her "North Star" in her activism for Muslim reform.

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"You cannot ever forget the evil that was expressed on 9/11, because of the ripple effects of this day," she said. "Danny [Pearl]'s mom died this year without ever being able to see her son returned from Pakistan as a result of the ripple effect of 9/11 – and so many sons and daughters don’t know their parents because their blood has been shed into the lands of Afghanistan."

Earlier this year, a Pakistani court ordered the release of Ahmad Saeed Omar Sheikh, who had been convicted and then acquitted upon appeal of playing a role in Pearl's abduction. 

In Afghanistan over the past several weeks, the Taliban pushed a propaganda charm campaign, presenting itself as more moderate and tolerant – but current and former U.S. officials, human rights activists, and refugees are worried their return to power will also mark a revival of their severe mistreatment of women.

"The new Taliban is very much the same as the old Taliban," former Ambassador Nathan Sales, the Trump-era head of the State Department’s Counterterrorism Bureau, told Fox News. "They still are committed to their partnership with al Qaida and they still work hand-in-glove with terrorists."

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They’ve even put wanted terrorists in government roles. Haqqani network leader Sirajuddin Haqqani, who has a $5 million FBI bounty on his head, is the new minister of interior.

"This is not your reformed Taliban that many in the West have been looking for," Sales said. "They are every bit as radical and every bit as committed to violence as they were in the run up to 9/11."

However – militarily and through diplomacy and intelligence – he said the U.S. is more prepared to thwart the next attack than it was 20 years ago.

"We are more safe and more secure today than we were on 9/11," he said. "We are much better at counterterrorism than we were before. Our military is much better at finding and fixing and finishing bad guys on the battlefield."

He also said U.S. sanctions enforcement has gotten more effective over the past two decades, as has foreign surveillance. 

"All that said, the question is not whether the United States has the capability to fight terrorists, the question is whether our political leaders have the will to continue to focus on this problem," he said.

Even after leaving Afghanistan, he said, "terrorists get a vote on whether to continue" attacking Americans around the globe.

"So we are more secure now than we were 20 years ago," he said. "But my fear is that the decision to leave Afghanistan to its fate without any sort of military capabilities there to continue to fight terrorists is putting us in a weaker position than we were in just a couple of months ago."

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The Biden administration’s abrupt withdrawal caught many people around the world off guard – including thousands of Americans and tens of thousands of Afghan allies who had to try and scramble to escape the country as Taliban forces swept across the nation and seized nearly all of its territory ahead of the Aug. 31 deadline.

There were reports of militants going door to door, killing or kidnapping people who had worked with the U.S. Civilians trying to reach Kabul’s international airport to evacuate found themselves beaten at Taliban checkpoints. And an ISIS-K suicide bomber killed 13 U.S. service members and dozens of Afghan civilians outside an airport gate.

"The war is not over," Nomani said. "And it is the ideological war that we have to win."

Fox News’ Lucas Tomlinson and Audrey Conklin and The Associated Press contributed to this report.