Units and sub-units will remain in march formation for as long as is reasonable in order to maintain tactical momentum, as this formation facilitates speed of movement, command and control.
Regiments will generally march along one or two routes, battalions will march along a single route.
Units and sub-units in march formation will organize with a reconnaissance element (combat reconnaissance patrol) forward followed by an advanced guard or forward security element. Flank security will move alongside the route. The main body will trail the recon elements and be followed by a rear security element. If the reconnaissance elements come into contact, the unit or sub-unit will either bypass or have the reconnaissance element fix the contacted force while the main body maneuvers into an advantageous attack position.
The following templates were taken from U.S. Army Field Manual 100-2-1 (1984). Left clicking on the images will expand them into new windows.