(CNN) -- Lt. Gen. Stanley McChrystal is a man of many secrets.
Lt. Gen. Stanley A. McChrystal has been nominated as commander of forces in Afghanistan.
Every day at 6:30 a.m., McChrystal, a former special operations chief slated to become the top American commander in Afghanistan, chairs one of the most classified meetings in Washington. Senior military officers gather behind this door to discuss what has happened in the world overnight
McChrystal hasn't let a reporter inside the room. In recent years, he's rarely spoken publicly.
Now, the question is whether McChrystal's largely secretive career will help or hurt his bid to win Senate confirmation as the next commander of forces in Afghanistan. McChrystal is appearing before the Senate Armed Services Committee this week to answer questions about how the U.S. military will handle the counterinsurgency that has erupted in Afghanistan and help the country rebuild.
Last month, Defense Secretary Robert Gates fired Gen. David D. McKiernan, the former U.S. and NATO commander in Afghanistan, and selected McChrystal as the replacement candidate. Gates said he wanted "fresh eyes on the problem" in Afghanistan. Watch how McChrystal's nomination is being eyed »
If selected, McChrystal will have the daunting challenge of winning the support of the Afghan people while killing off the growing Taliban threat once and for all.
Some officials say McChrystal, who has been a senior official on the staff of Chairman of the Joint Chiefs of Staff Adm. Michael Mullen, holds extensive experience in counterinsurgency warfare. This experience will be critical to reshaping U.S. military efforts in Afghanistan.
But in the last few years, McChrystal's involvement in leading covert commando units when he headed the Joint Special Operations Command at Fort Bragg has raised some concerns.
Most of McChrystal's military career has been classified. He left the Pentagon in 2003.
"Many of the collateral damage incidents in which Afghan citizens -- civilians -- have been killed have been associated with special forces operations in parts of the country where we didn't have a large ground force presence," said Steven Biddle, a senior fellow for defense policy with the Council on Foreign Relations.
The covert units became subject of controversy in 2004 following the friendly fire death of Army Cpl. Pat Tillman.
The Army's Criminal Investigations Division and the Defense Department's inspector general investigated the case, concluding that officers in Tillman's chain of command knew almost immediately that the former NFL star had been killed by fire from his own platoon. The information was withheld from his family for more than a month, which violated Army regulations.
McChrystal was one of four generals identified in the report. He was later cleared in the investigation but was faulted for not immediately notifying Tillman's family of suspicions that it was a friendly fire incident.
Tillman's parents have said McChrystal's record should be reviewed.
There are also concerns that McChrystal's troops mistreated prisoners in Iraq and Afghanistan, a senior congressional staffer told CNN. But the Senate Armed Services Committee questioned McChrystal last year and cleared him.
In his career spanning more than three decades, McChrystal has gone after high-profile targets including Saddam Hussein and Hussein's sons, Uday and Qusay Hussein. He also hunted terrorist leader Abu Musab al-Zarqawi in Iraq -- slain in a U.S. airstrike in 2006 -- and and the world's most wanted man, Osama bin Laden.
"I view Gen. McChrystal as crucial, I mean as a critical player in the hunt for bin Laden," said Fran Townsend, former presidential adviser for homeland security. Townsend worked with McChrystal closely on security matters.
The challenge facing McChrystal now is whether a soldier who has spent his career leading men in hunting terrorists will be able to command a war that now focuses on rebuilding a shattered Afghanistan.
CNN's Barbara Starr contributed to this report.