Covering Force Actions vs. Defenses in Depth

Last night, I promised that I would address the difference between a covering force action and a defense in depth, and why I am now persuaded that the tactic used by John Buford at Gettysburg was actually a covering force action and not a defense in depth. Here goes…..

I find it easier to use modern military definitions to define these terms. Even though they use modern parlance and anticipate modern weaponry, they still apply equally well to Civil War tactics.

The Pentagon defines a defense in depth as this: “The siting of mutually supporting defense positions designed to absorb and progressively weaken attack, prevent initial observations of the whole position by the enemy, and to allow the commander to maneuver the reserve.”

In other words, a defense in depth requires that a defender deploy his resources, such as fortifications, field works and military units, both at and well behind the front line, falling back from one defensive position to another, with the whole idea being to suck the enemy in so that he exposes his flanks to attack. The strategy is especially effective against an attacker who is able to concentrate his forces to attack a small number of places along an extended defensive line. It employs the deployment of force in mutually supportive positions. In other words, the idea is to force the enemy to drive the defender from each chosen position and inflict casualties upon him in the process.

A recent U. S. Army manual defines a covering force action thusly: “The covering force operates independently from the main body. The purpose of covering force operations is to develop the situation early and deceive, disorganize, and destroy enemy forcing. However, unlike screening and guard forces, a covering force is tactically self-contained and often seeks to become decisively engaged with the enemy. Cover operations are performed in the offense or defense and can be conducted by either the ACR or separate brigade.

When a covering force action begins, the main body generally is not engaged. Depending on how much warning it gets, and the mission of the main body, the covering force can be heavily augmented with engineers, MI, and artillery before the battle begins. With less warning, support arrives with the battle already underway. In any event, the covering force is expected to continue resistance until the corps has had time to deploy. Because it operates independently from the corps main body, the MI company must be able to move all of its personnel, systems, and equipment with its own organic assets.”

In other words, the idea behind a covering force action is to trade time for space, thereby allowing a detached forward unit (usually cavalry) to delay the advance of the enemy long enough to permit the main body to come up and engage. The covering force will operate independently of the main body.

Two examples of defenses in depth come to mind. General Daniel Morgan designed and implemented an excellent defense in depth that was used to great effect at the Battle of Cowpens. This tactic, which used militia to draw in Tarleton’s men, then exposed them to a galling fire from the main line and then to a cavalry charge into the flank. Nathanael Greene used the same tactic effectively at Guilford Court House, although Greene was eventually defeated.

In the Civil War, Lt. Gen. William J. Hardee designed a defense in depth very similar to–some say inspired by–Morgan’s defense in depth at Cowpens that he used effectively at the Battle of Averasboro on March 16, 1865. Hardee, with less than 10,000 men, was able to hold off half of Sherman’s army for an entire day by using a well-designed defense in depth. He used three prepared defensive positions to do so, falling back from each one as he was driven from them, until he ultimately reached the third, and final, line. By that time, it was dark, and Sherman didn’t have the stomach to attack that line. Hardee then pulled out during the night.

What John Buford designed and implemented at Gettysburg was a classic example of a covering force action, one that was, in fact, such a perfect textbook example of one that it’s taught as a staff ride by the Army to this day. The whole idea was to trade three ridge lines worth of space for time to permit Reynolds and First Corps to come up and engage. Buford’s tactic delayed the Confederate advance for nearly five hours on the first day of the Battle of Gettysburg.

Having studied all of this in much greater depth, I came to the conclusion that my prior assertions about Buford using a defense in depth was just plain wrong, and I’ve said as much publicly many times. It was, indeed, a perfectly designed and perfectly executed covering force action.