Following a battalion command position in the 25th Infantry Division in Hawaii in the mid-1990s, Caldwell was sent to Haiti to work as political-military liaison in the U.S. Embassy during Operation Uphold Democracy.

After his tour in Haiti, he commanded the 1st Brigade, 10th Mountain Division, at Fort Drum, New York.
He worked in the Office of the Director for Strategic Plans and Policy on the Joint Chiefs of Staff at the Pentagon, and later served as the executive assistant to the Chairman of the Joint Chiefs of Staff.

Caldwell was serving as deputy director for operations, U.S. Pacific Command, Hawaii, at the time of the 9/11 attacks, when  the command's focus shifted from regional war plans to the Global War on Terrorism.

In July 2002 Caldwell was assigned as senior military assistant to the deputy secretary of defense, Paul Wolfowitz.
In this position he served his boss during the preparation, execution, and follow on for the Iraq War's Operation Iraqi Freedom and other aspects of the Global War on Terrorism.

From May 2004 until June 2006 Caldwell served as the Commanding General of the 82nd Airborne Division.
As the division commander, Caldwell oversaw deployments by the units under his command to both Afghanistan and Iraq, as well as disaster-relief efforts following Hurricane Katrina in New Orleans.
Following a battalion command position in the 25th Infantry Division in Hawaii in the mid-1990s, Caldwell was sent to Haiti to work as political-military liaison in the U.S. Embassy during Operation Uphold Democracy.
After his tour in Haiti, he commanded the 1st Brigade, 10th Mountain Division, at Fort Drum, New York. He worked in the Office of the Director for Strategic Plans and Policy on the Joint Chiefs of Staff at the Pentagon, and later served as the executive assistant to the Chairman of the Joint Chiefs of Staff.
Caldwell was serving as deputy director for operations, U.S. Pacific Command, Hawaii, at the time of the 9/11 attacks, when  the command's focus shifted from regional war plans to the Global War on Terrorism.
In July 2002 Caldwell was assigned as senior military assistant to the deputy secretary of defense, Paul Wolfowitz. In this position he served his boss during the preparation, execution, and follow on for the Iraq War's Operation Iraqi Freedom and other aspects of the Global War on Terrorism.
From May 2004 until June 2006 Caldwell served as the Commanding General of the 82nd Airborne Division. As the division commander, Caldwell oversaw deployments by the units under his command to both Afghanistan and Iraq, as well as disaster-relief efforts following Hurricane Katrina in New Orleans.
William B. Caldwell IV