Part 1 here
Choice of forces
The control of the sea equivalent to ground forces' "control of terrain" can be done by surface warships and submarines while the control of the air equivalent to ground forces' "control of terrain" can be done with fighters. There's little reason to believe that dismounted forces have a monopoly on exercising control of terrain if so very different forces serve equivalent roles on different terrains.
In fact, it's rather terrain-specific, as is combat as well. The myth hat only infantry can hold and control terrain is rooted in economics rather than fact: Back in WW2 only infantry was affordable in the quantities required to be on guard, controlling and holding terrain. This led to infantry serving in that function even in desert terrain, though at times equipped with powerful anti-tank guns (or gun-howitzers) at platoon level.
The wars of Israel ('67 and '73) and the Iraqi attempt to defend with dug-in tanks in 1991 show that tanks can indeed be used to hold and control terrain. The Iraqi's lack of success in their example was a phenomenon universal to the conflict and not to be blamed on the tactic of static defence with hull down tanks.
A most static approach like this doesn't fully exploit the strengths of tanks, of course. You can do more with less using a more efficient tactic, and this too was done.
In late 1942 and early 1943 a single motorised division with weak reinforcement by AFVs defended a frontage of more than 100 km for weeks in the steppe terrain south of Stalingrad. As far as I know it did so by following not written doctrine, but principles of German land forces at the time: A motorised line of pickets that reported by radio, and serial (one after another, never parallel) engagements at shifting divisional Schwerpunkte to strike at intruders with success. Their weeks-long defensive mission there was probably the birth of modern low force density fully motorised mobile defences.We sure cannot follow the Afrikaarmee's example of establishing heavily armed infantry strongpoints with as a defensive front. We simply wouldn't have the infantry numbers until we mobilised for a year or so.
Meanwhile, there's no doubt that infantry is the first if not only choice to control terrain on infantry-friendly terrains. Nobody is going to control extended woodland terrain with a tank company anytime soon.
To sum it up; dismounted forces are the first choice for the control of terrain mission in infantry-friendly (short lines of sight or very soft ground) and mounted forces are first choice for the control of terrain mission in tank-friendly terrain.
"Control the terrain in this area" is an awfully standardised mission and even taking into consideration all those other military missions this allows only for a crude description.
It is conceivable that a much wider range of ambitions would make sense under certain circumstances. Let's assume there's an independent/ militia (light infantry) battalion in some hilly terrain with woodland on hilltops and often small rivers, lakes or settlements in the valleys in between. Typical Central and Southern German terrain, that is. The battalion has to cover a large area there, and no doubt its abilities in combat depend a lot on what effort the hostile forces project into this area. It could not "hold the ground" against a mechanised division, for example. Meanwhile, it could intercept and reduce armoured reconnaissance forces.
Let's conceive what different levels of ambition could be given as area missions to this battalion from a superior CO:
(1) Stay alive (a necessary prelude to further action 'behind enemy lines', such as within the Jagdkampf doctrine)
(2) Observe and report
(3) Observe, investigate and report
(4) Observe, investigate, report and conduct counter-reconnaissance (recce platoons of three light AFVs would be ambushed and hunted down)
(5) Observe, investigate, report and harass (harassment would include ambushes and raids against all hostile forces)
(6) All of the above plus destroy small forces (forward deployed aviation elements, forward supply dumps and forward area air defence missile units would be destroyed rather than only hurt)
(7) All of the above plus delaying actions (raising obstacles, forcing advance guards to deploy for combat then disengage, immobilising lead vehicles on narrow routes etc.)
(8) Defend (against any attacks)
(9) Yield no ground without permission (the typical Stalin and Hitler amateur CinC nonsense)
(10) Tolerate no hostile forces in the area (requiring offensive action against those already present)
"Control terrain" and "hold terrain" cover ambitions four to nine. More degrees of ambition can be made up any time, so I suppose it's clear now why I think the established mission types are crude and unspecific. moreover the typical indoctrination tells dismounting forces that they have a monopoly on holding terrain without bringing home how many different degrees of ambition are possible and may need to be used depending on the situation.
Low force density
As so often, strictly limited resources may lead to low force densities - such as a single mechanised brigade with a few hundred dismounts being on its own in a 50 x 50 km area. A Polish defensive posture against Belarus during a Baltic Defence scenario would likely see no more than three brigades covering the 250 x 150 km area in Poland's East (crucial for the security of the Polish capital of Warsaw), for example.
This is a difficult mission assuming no science fiction drone/robot army is available. An actual observation of much terrain with short lines of sight would be impractical. Pickets in settlements could keep main streets under surveillance, pickets elsewhere could keep roads and generally open terrain under surveillance. Hostiles that slipped through after detection would need to be either ignored (particularly if they are moving homewards) or search parties would be sent out to re-establish contact and shadow them till some quick reaction force/strike element or air attack eliminates this particular intrusion.
Meanwhile, some promising ways to deal with major intrusions (battalion battlegroups or bigger) would be
(1) delaying action with mounted forces and very much close air support
It's unlikely that enough CAS would be available, as the example of Khafji showed us that very much would indeed be necessary.
(2) delaying action with mounted forces and mounted counterattack
As mentioned in the 1942 example above, it's best to do this serially, dealing with one crisis after another instead of splitting up the reserves available for counterrattacks. This is a basic application of the Schwerpunkt idea in its German interpretation.
Delaying actions are necessary to buy the time for such a serial reaction to multiple major intrusions. The balance between massing reserves for Schwerpunkt actions and dispersing strength for delaying actions of the Schwerpunkt would need to be driven by this timing problem; 'enough for delaying, as much as possible for the reserves'.
(3) Counteroffensive elsewhere, betting that the opposing forces commander aborts his own offensive in response (Belarus could afford losing Minsk less than NATO could afford temporarily losing Warsaw, of example). This is almost impossible due to political restrictions unless the warzone is actually not dear to the politicians and citizens at all (such as most of the Saudi Arabian desert terrain wouldn't have been important to Americans in 1990).
(1) and (2) include "control of terrain" missions, whereas in (3) this would merely be relevant at the beginning. Dealing with intrusions of superior forces demands that either the ambitions be limited (see above) or additional forces (CAS, ground forces reserves) be introduced to the area to deal with the threat.
This trivialises the "control the terrain" mission somewhat: The mission is impossible to accomplish against (yet unknown) superior opposing forces, and rather disingenuous against inferior opposing forces. "Go there, do what you want" would often times be as good a mission as "control the terrain". This assumes that "control the terrain" would actually be given as mission, and honestly, I doubt that its prominence in wartime (excluding wars of occupation) would come anywhere close to its prominence in field manuals. It's usually much more sensible to simply assign an area of operations to a subordinate force and tell its CO that an attacking OPFOR must not traverse this area in less than x hours. "Control of terrain" is more of an activity than suitable for a mission order. I mentioned its characterisation as a mission as curious in part 1 already.
Potential of air power
In theory you could control terrain with air power alone, given sufficient resources. This is going to be efficient in rare cases only. Patrol aircraft with the ability to engage and disable soft vehicles could have secured the Afrikarmee's Southern flank (Sahara desert) against the reconnaissance and raiding missions of the Long Range Desert Group, for example.
Air power adds the third dimension and thus typically has more terrain in field of view than observers on the ground. Only foliage and the roofs of buildings are (near-)perfect blocks to its line of sight. The potential to substitute for pickets and patrols is thus visible. Maybe in the long term small flying drones can saturate a warzone and report all present opposing forces (and civilians).
The strike part of denying terrain to the opposing forces can be met by air power as well, at least in principle. It gets impractical real quick in woodland and built-up areas, unless you assume an armada of small (lethal) flying drones again. They'd need to be able to navigate through woodland and buildings (including open doors or windows), though.
Civilians are typically ignored in the context of "control of terrain"-related writings, but I suppose a battalion CO tasked to control a 10 x 10 km terrain would badly disappoint his superior if another transiting force found all roads blocked by traffic jams, or even hostile police forces and ruling party officials organising civilian construction of obstacles and disabling of bridges et cetera - all while that terrain is "being controlled" by aforementioned battalion. "Control of terrain" will thus usually include a lot of what's known as "civ-mil relations" activities, and this will be one more drain on personnel and vehicle resources. This may be an overwhelming problem if the terrain to be controlled is a hostile power's city or even megacity.
The Russians only got Chechnya under control for good when they flooded it with more military and paramilitary troops than Chechnya had civilians prior to the wars. This style is not going to be an option is most cases.
The recent wars of occupation and even the invasion of Iraq in 2003 showed that civilians or combatants hiding among civilians can emerge and strike, vanishing afterwards. Such a very elusive opposition defies attempts "to maintain physical influence over a specified area to prevent its use by an enemy", of course. Even years of efforts may be insufficient to accomplish such a mission in face of such an opposition unless you wade deep into war crimes territory. This, too, should serve as a call for modesty in the ambitions. The definition as given by the U.S.Army is too ambitious, too absolute - and thus in many cases utterly impractical. It's equivalent to the radical most ambitious mission #10 mentioned earlier while hiding its extremist nature behind a seemingly not so aggressive wording.
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It shouldn't surprise that I looked at "control of terrain" through the same lens as at plenty other topics before; the role of dispersed forward forces in conventional warfare is my pet topic. I picked the topic of "control of terrain" for a reason.
I made my case that military theory and doctrine can become more advanced, more realistic and more detailed in the case of "control of terrain" in land warfare. The present state of the art is rather crude, and too much under influence of days long gone by, when plenty infantry was available on day one of a conflict. Limited resources require a high efficiency of their employment, and appropriate modesty in the ambition and in their missions.
related Defence and Freedom blog posts:
I'm not motivated for this list today, but no doubt all of them have the "Military theory" tag.