The United States has detained more than 83,000 foreigners in the four years of the War on Terror, enough to nearly fill the NFL's largest stadium.

The administration defends the practice of holding detainees in prisons from Afghanistan to Guantanamo Bay as a critical tool to stop the terrorist insurgency in Iraq, maintain stability in Afghanistan and get known and suspected terrorists off the streets.

Roughly 14,500 detainees remain in U.S. custody, primarily in Iraq.

The number has steadily grown since the first CIA paramilitary officers touched down in Afghanistan in the fall of 2001, setting up more than 20 facilities including the "Salt Pit," an abandoned factory outside Kabul used for CIA detention and interrogation.

In Iraq, the number in military custody hit a peak on Nov. 1, according to military figures. Nearly 13,900 suspects were in U.S. custody there that day — partly because U.S. offensives in western Iraq put pressure on terrorists before the October constitutional referendum and December parliamentary elections.

The detentions and interrogations have brought complaints from Congress and human-rights groups about how the detainees — often Arab and male — are treated.

International law and treaty obligations forbid torture and inhumane treatment. Classified memos have given the government ways to extract intelligence from detainees "consistent with the law," administration officials often say.

On Capitol Hill, Sen. John McCain, R-Ariz., is leading a campaign to ban cruel, inhuman or degrading treatment of prisoners in U.S. custody. The administration says the legislation could tie the president's hands. Vice President Dick Cheney has pressed lawmakers to exempt the CIA.

"There's an enemy that lurks and plots and plans and wants to hurt America again. And so you bet we will aggressively pursue them. But we will do so under the law," President Bush said last week.

Some 82,400 people have been detained by the military alone in Afghanistan and Iraq, according to figures from officials in Baghdad and Washington. Many are freed shortly after initial questioning.

To put that in context, the capacity of the Washington Redskins' FedEx Field, the NFL's largest, is 91,704. The second largest, Giants Stadium, holds 80,242.

An additional 700 detainees were sent to Guantanamo Bay, Cuba. Just under 500 remain there now.

In Iraq, the Defense Department says 5,569 detainees have been held for more than six months, and 3,801 have been held more than a year. Some 229 have been locked up for more than two years.

Many have been questioned by military officials trained at the main U.S. interrogation school, Fort Huachuca in Arizona. Pentagon officials say those mistreated are relatively few when the sheer numbers are considered.

Yet human rights groups say they don't know the extent of the abuse. "And there is no way anyone could, even if the military was twice as conscientious. It is unknowable, unless you assume that every act of abuse is immediately reported up the chain of command," said Tom Malinowski, Washington director for Human Rights Watch.

As of March, 108 detainees were known to have died in U.S. military and CIA custody, including 22 who died when insurgents attacked Abu Ghraib and others who died of natural causes. At least 26 deaths have been investigated as criminal homicides.

Last week, Senate Armed Services Chairman John Warner, R-Va., said that more than 400 criminal investigations have been conducted and 95 military personnel have been charged with misconduct. Seventy-five have been convicted.

Through the CIA, a much smaller prison population is maintained secretly by the agency and friendly governments. A network of known or suspected facilities — some of which have been closed — have been located in places including Thailand, Central Asia and Eastern Europe.

The governments of Thailand and a number of Eastern Europe countries have denied the CIA operated prisons within their borders. The agency consistently declines to comment.

About 100 to 150 people are believed to have been grabbed by CIA officers and sent to their home countries or to other nations where they were wanted for prosecution, a procedure called "rendition." Saudi Arabia, Jordan and Egypt are known to cooperate.

The practice has taken on a negative connotation, but that wasn't always the case. In a December 2002 speech touching on intelligence successes, former CIA Director George Tenet said the agency and FBI had "rendered 70 terrorists to justice."

While officials won't confirm the number, another two to three dozen "high-value" detainees are also believed to be in CIA custody. Among them, Khalid Shaikh Mohammed, an alleged mastermind of the 9/11 attacks.

As House Intelligence chairman in 2004, CIA Director Porter Goss took a strong stand on some of the gray areas of detention practices. In an AP interview, he said, "Gee, you're breaking my heart" in response to complaints that Arab men found it abusive to have women guards at the Guantanamo Bay prison camp.

Before Goss took over the agency, its inspector general completed a report on the treatment of detainees, following investigations into at least four prisoner deaths that may have involved CIA personnel. To date, one agency contractor has been charged.

The inspector general's report discussed tactics used by CIA personnel — called "Enhanced Interrogation Techniques." Former intelligence officials, who spoke on condition of anonymity because the practices are classified, say some interrogation techniques are well-known: exposing prisoners to cold, depriving them of sleep or forcing them to stand in stressful positions.

Perhaps the most publicly controversial technique is waterboarding, when a detainee is strapped to a board and has water run over him to simulate drowning.