GUANTANAMO BAY NAVAL BASE, Cuba — Five Guantanamo prisoners charged in the Sept. 11 attacks returned before a military tribunal Monday, forgoing the protests that turned their last appearance into an unruly 13-hour spectacle.

But the apparent cooperation of Khalid Sheikh Mohammed, who has said he planned the worst terror attack on US soil, and four codefendants did little to speed up proceedings that have been stuck in a legal and political morass for years.