We have the five domains of the land, the air, the seas (and if you really wanted to, you could separate the seas into a surface and a sub-surface domains quite validly), space, and cyber-space. How do they fit with each other?
The basic domain is the land where people live. In the beginning there were only ground forces to control the land, from bands of men and then up to armies.
The next domain is the sea, which people soon learned to use for resources, bulk cheap transportation, and trade, and then for amphibious warfare. The sea is worth controlling just for itself, but recall that ultimately control of the seas is for its impact on the land. Resources are landed to be used by the people on the land. People and resources are transported between points on the land. Trade is between points on the land. And amphibious warfare is to take the land.
For those in doubt about the ultimate purpose of the Navy, recall that in the post-Cold War world when control of the seas was assured after the Soviet fleet collapsed, the Navy began their "... From the Sea" approach to projecting power from the sea to the land. The Littoral Combat Ship was intended--but not robust or cheap enough for--sailing and fighting close to the shores. The core mission of controlling the seas must lead to projecting power to the land for control of the sea to make sense.
For many centuries, the land and sea were the only domains.
The air domain began to support operations--first with observation and then kinetics and expensive transport of high priority items--over the land and then expanded to support operations over the seas. So controlling the skies is purely for the effects of supporting friendly operations on the land and at sea by attacking enemies on the surface and denying that ability to enemies.
Space is a higher version of the air domain. It is still mostly an observation domain that is at the infancy of fighting to control the domain and using it for observation and then kinetics rained down from space.
And cyber-space is all the rage these days. It is surely important. But its point is to affect people (by attacking their connected things) in the physical domains, whether in the land, sea, air, or space.
Remember, as the original domain force, the Army if alone would have to fight in the land, sea, air, space, and cyber-domains because all the domains impact the land. (And this mostly applies to the Navy as the second senior service.)
The Army has fielded anti-aircraft and coastal defense weapons to fight in the air and sea domains; and has bigger missiles to fight weapons coming from the space domain and even works to fight in the cyber domain, of course.
But other services that could better focus on their domains at sea and in the air were created. Eventually there will be forces dedicated to space and cyber, I imagine, when their capabilities are more fleshed out.
So that's the starting point from my point of view. What does multi-domain battle really mean, then?
The Army wants the other services to endorse its Multi-Domain Battle concept for combined operations across all domains — land, sea, air, space, and cyberspace — against high-end adversaries like Russia and China. The goal is to get a multi-domain concept co-signed by all four branches by October 2019. To get there, the Army has to listen to its sister services and revise its ideas.
And an Army plan has to fully incorporate what other services (including some not yet fully independent) do without insisting that they immediately rush to the sound of the guns on the land, as Army planners in the 1990s realized:
We learned quickly not to use an Army game to solve the problems of the Department of Defense. Never be ashamed to call an Army strategic game what it is: a game focused on landpower. Sure, a whole of government approach is vital for winning wars. Jointness is imperative. No single service fights alone. But the game must view jointness from a land-power perspective.
Yet we must be careful not to be too parochial in crafting the game. The validity of the game will be challenged if it becomes so exclusive to the ground forces that it exercises only in one dimension. This imperative is even more important as we add more dimensions to our calculus such as cyber, space, and interagency involvement.
So in theory the other domains must be won even as the Army struggles in its domain.
And the Army can surely help in other domains--as it would if no other services had the primary role--in efforts that don't directly affect the land domain.
Yet while the other domains ultimately need to be exploited for their ability to affect operations on the surface of the planet (that is, the domains of the Army and Navy), the Army can't forget that while the Army has the core competency of fighting for the land domain (not to leave out the Marine land forces, but they are more of a vital bridge between sea and land domains), the other domains need to be fought for and won before they can affect the land domain where the Army needs help. The Army can't skip past those supremacy operations and skip right to the good part where power is projected from the other domains to the land.
But my deepest fear is that reasonable cross-domain jointness that ultimately recognizes that controlling the surface of the planet--sea and land, but ultimately the land is most critical will be lost.
My fear is that the Army will be swamped by the services who fight for the sea, air, space, and cyber domains and drawn into supporting other service operations to secure their domains without then projecting power to support the Army in the land domain.
My fear is that the reasonable focus of other services on achieving dominance of their domains will lead them to believe they can win wars within their domains alone without needing the Army to do more than mop up the crushed remnants of our enemies staggering about dazed by whatever power is projected from the sea, from the air, from space, or from cyber.
America has a history of trying to use technology to reduce Army casualties as much as possible. The danger is that this tips over into trying to use technology to replace the need for the Army at all as the ultimate Army casualty reducer.
My fear is that other domain forces will continue to speak with their own distinctive parochial accents despite the tutelage in speaking jointly across the domains; and that multi-domain operations will be a one-way street of harnessing Army capabilities as auxiliaries for the fights in the non-land domains.
Perhaps I am wrong to fear this and that all will work out well. But my confidence level is low.
