The 506th Infantry Regiment, originally designated the 506th Parachute Infantry Regiment (506th PIR) during World War II, is an airborne light infantry regiment of the United States Army. Currently a parent regiment under the U.S. Army Regimental System, the regiment has two active battalions: the 1st Battalion, 506th Infantry Regiment (1-506th IR) is assigned to the 1st Brigade Combat Team, 101st Airborne Division, and the 2nd Battalion, 506th Infantry Regiment (2-506th IR) is assigned to the 3rd Brigade Combat Team, 101st Airborne Division.
The regiment served with the 101st Airborne Division in World War II. Regimental elements have served with the 101st in Vietnam, Iraq, and Afghanistan. Regimental elements have also served in peacetime with the 2nd Infantry Division, and deployed to Operation Iraqi Freedom.[3]
*via WIKIPEDIA