When the Marines defend their huge investment in Close Air Support, it’s largely because they need it. They simply don’t have a lot of tube artillery available for support. Why? Because they will never have enough amphibious shipping to move it.
The Army, on the other hand, has since the middle of the 19th Century had a long tradition of excellence in artillery, and accordingly places a lot of faith in a lot of guns.
Let’s compare some of the fire support available to a division. Organic to the Marine division is an artillery regiment. In the late 1980s and early 1990s, this regiment had three battalions of light artillery, 105mm tubes, and one battalion of 155mm artillery. All four battalions had towed pieces.
At first glance, Army artillery seems quite comparable. A light division had “Division Artillery”~ effectively a brigade, with three battalions of 105mm guns, and one battalion of 155mm guns, all towed. Seems pretty comparable.
But if we leave the light divisions, and look at the Army’s heavy divisions, we see a somewhat more robust organization. Each mechanized or armored division had a similar organization, but different armament.
Heavy divisional DivArty had three battalions of self-propelled 155mm guns (each with a self-propelled ammo carrier). It also had a battalion of self-propelled 203mm (8”) guns. Eventually, the 8” battalion would be replaced by a single battery of MLRS 270mm rocket launchers.
But the story doesn’t end there. Army divisions in Europe were intended to fight as a part of a corps, and indeed, as a part of a field army. And a great deal of the combat power of a corps or field army is located in units outside of the divisions. Each heavy corps typically had two separate artillery brigades, each with four battalions, usually three of 155mm and one battalion of MLRS, as they phased out the 8” tubes.
One of the key precepts behind US Army artillery doctrine has always been concentration. If it’s worth shooting at, it’s worth shooting at a lot. So it would be typical for the main effort of a corps operation to receive the support of both corps artillery brigades. And within that main effort division, it would be typical for the maneuver brigade forming the main effort to receive the support of all the guns of both the division and the corps artillery, or at least a priority claim to their fires.* Conceivably, one maneuver brigade of three battalions would have the support of 12, or even more, battalions of artillery. That’s a level of fire support a Marine regiment commander could only dream of. And that doesn’t count the attack helicopter and Air Force tac air support our notional Army brigade might receive. And because all these heavy artillery brigades were self-propelled, they could rapidly shift support from one area to another.
With the collapse of the Soviet Union, the Army no longer faces the spectre of a single division having to stem the onslaught of an entire Russian tank army. And the past decade of limited warfare in Iraq and Afghanistan has seen a much smaller need for massed artillery fires.
Instead, today’s artillery has shifted emphasis from massing fires to longer ranges and greater precision, via such tools as rocket assisted projectiles, guided unitary warhead MLRS rockets, and guidance kits for conventional 155mm artillery that permits a limited “boost/glide” profile. The battlefield a single maneuver brigade occupies is much larger than in years past, even as little as 20 years ago. And simply to cover that area, the supporting artillery either needs a longer range, or the greater lethality of guided rounds (that way, smaller units of artillery, such as a battery or even just a platoon can disperse over a wider area to support more units and cover more battlespace).
*I’ll leave it to URR or Esli to explain the doctrinal niceties of attached, OPCON, Direct Support, General Support, or General Support Reinforcing.