Islambad, Pakistan ? Khalid Sheikh Mohammed’s capture four years ago didn’t shut down al-Qaida or bring the Americans to Osama bin Laden.

But if his mega-confession is to be believed, his arrest was a crushing blow to bin Laden’s plans for even more deadly attacks in the wake of Sept. 11, 2001. His expertise was never replaced and his absence has contributed to the group’s transition from a fear-inspiring attack force to a hate-filled voice on the Internet, urging others to wage terror against the West.

“In terms of competence for managing, planning and executing terrorist attacks, KSM was the best in al-Qaida,” said Rohan Gunaratna, a terrorism expert and author of a book on al-Qaida. “That’s why Osama bin Laden and other important al-Qaida leaders entrusted him with so many operations.”

In his testimony to a military tribunal at Guantanamo Bay, released in redacted form Wednesday by the Pentagon, Mohammed claimed involvement in 31 attacks and plots.

Some are almost surely true.

“He’s a boastful character. I think after four years of silence, he’d probably like to be up there with the likes of bin Laden and Ayman al-Zawahri as a major figure and ideologue, and impress people with everything he’s done,” said Ahmed Rashid, a Pakistan-based author on Islamic militancy.

He “sang” to interrogators almost from the start, after his March 2003 arrest at a house outside the Pakistani capital. Much of the information in the 26 pages of released testimony has been long known.

But even if his self-proclaimed status is somewhat exaggerated, he “gave the Americans lots of information about what kind of ideas al-Qaida had, and how they put their plots together,” said Magnus Ranstorp, a terrorism expert at the Swedish National Defense College.