The Army has changed drastically for the 21st century. During the 20th century's Vietnam War, a "Leg Outfit", just boot leather (No M-113 APC/ACAV-Armored Personnel Carriers/Armored Cavalry Assault...
The Osprey Military Order of Battle Series for the WWII Ardennes Offensive list about 3,200 men for a typical infantry regiment. This number would be adjusted depending on attached and detached units...