The Reverse Slope Defense

While discussing Okinawa the other day, I mentioned the Japanese forces masterful use of the reverse slope defense.

The wise commander uses terrain as another tool in his kit, taking it into consideration along with the Mission, Enemy, Troops, Time available, and Civilian consideration. If you are ordered to defend, and your enemy has stronger direct and indirect fire weapons than you, a reverse slope defense may be advised. So what is the reverse slope defense?

A reverse slope defense is a technique in which the defending force is positioned on the far side of any elevated terrain from the attacker. Take the picture below as an example:

call_1-88_fig1

The reverse slope defense:

  1. Typically used when the attacker has greater firepower.

  2. Allows the defender to deny long range direct fires.

  3. Denies the attacker observation of the defense.

  4. Often uses an obstacle just below the reverse slope military crest to deny the attacker momentum.

Often the defender will have pickets and outposts on the forward slope to call artillery and mortar fires on the attacker as he approaches. The defender may choose, however, to instead ambush the attacker just as he crosses the crest of the terrain.

Often in mechanized combat, terrain features far more subtle than that in the figure above are used.  I served as the Opposing Force several times in the Pinon Canyon training site and each time, we would establish a reinforced platoon in the defense, against which a reinforced mechanized infantry/tank company team would attack.  Although our positions were on the highest ground on the battlefield, it was actually a reverse slope defense. The slightly steeper lower slopes meant that the attacking force could not see the high ground until he had reached a false summit approximately 1500 meters from our positions. And that’s just where we placed an obstacle belt of triple-strand concertina wire, an anti-tank minefield, and an anti-tank ditch. We’d also plotted pre-planned fires on several locations just forward of the obstacle. And as a nice touch, 15oo meters is just about the optimum engagement range for the Bradley’s 25mm cannon against light armor.

As the attacking company team approached, our dismounted infantry in advanced positions on the front slope could easily track him and provide us with plenty of early warning.  When the enemy approached the “crest” he was confronted by the obstacle belt. Forced to halt while preparing to breach the obstacle, the attackers were inevitably sitting in one of our artillery “kill boxes” and almost instantly had intense concentrations of artillery falling on his head.

As his engineers and mine-plow equipped tanks rolled forward to start their breach, they were easy pickings for our tank and TOW missile fires. The tanks and Bradleys supporting the breach effort were confounded because every time they came up to try to locate our positions, they too were instantly subjected to withering fires.

It wasn’t very often that a company team was able to breach our defenses on the first try.

Of course, the reverse slope defense isn’t always called for. Often, the defender will have greater long range direct and indirect firepower. In that case, he would probably maximize the engagement ranges of his weapons. Further, if an attacking force is able to rupture the lines of a reverse slope defense, the defender will be forced to displace to the rear. This negates the advantages of the defense, and often finds the defender pushed into the open, and subject to the same superior firepower of the attacker he was attempting to avoid in the first place. Several times during the Okinawa campaign, US forces struggled for days against small outposts, taking grievous losses. When they finally forced the Japanese to fall back to subsequent positions, the Japanese were forced into the open, and subject to slaughter by small arms, automatic weapons, mortars, artillery fire, naval gunfire, and airstrikes. It’s a lot easier to kill people in the open than dug into caves. And our troops took advantage of every opportunity to do so.

The reverse slope defense isn’t the answer to every military problem, but the wise commander always uses every possible advantage terrain gives him.