Overlapping Capabilities and Roles of Service Branches: An analysis

One of the curious feature of first-tier militaries, that that their different branches and arms occupy near-identical domains in terms of capability and mission role.

In an multi-series, I will try to explore this issue. In my first part, I will try to briefly seek out what kind of duplicative capabilities do various services possess.

In Part 2, I will analyse at how such overlapping roles and missions of service branches of non-western autocracies tend to be viewed by western observers at a means of “coup-proofing”.

In Part 3, I will briefly look at the Marine forces of Asia-Pacific countries, in terms of duplicative capabilities.

Part 1

An example of overlap would the Soviet Air Defence Forces, which not just possess its own array of AAA and SAMs, but a fleet of fighter jets that in numbers alone, easily dwarf the fleet strength of many other nations.

Interestingly, many large navies that have its own fleet of fixed wing aircraft, also tend to have its own aviation branch, examples include India, Japan, UK, Spain, Italy. In other cases, where rotary-wing aircraft, or better known as helicopters, are deployed to ships, the ownership and operation of said helicopters resided with the Air Force, for example, the Israel’s Defence Force.

There are two different potential causes when looking at this; do service branches develop in-house capabilites because of operational efficiencies (i.e it is better to keep everything in-house), or is it a matter of organizational politics, i.e inter-service rivalry between the different services?

There is also a matter of available funding.

The US is an outlier. Their Army has its own aviation branch, which admittedly consist mostly of helicopters, but in numbers alone, is larger than most countries’ air forces, and there have even been calls to permit the US army’s aviation branch to operate its own CAS fixed-wing aircraft.

On the flip side, the US Navy has its own aviation branch, and it’s sister service, the USMC, has its own aviation branch, operating not just its own aircraft that support Marine Ground operations, but also operating in domains that appear to be in the jurisdiction of the US Navy’s aviation branch, Marine Fighter Attack Squadrons, operating F-4 Phantom IIs, and F/A-18 Hornets, not just from land-based Marine bases, but from USN Aircraft carriers, such as flying off F-4 Phantoms and F/A-18 Hornets off US Aircraft Carriers.

Interestingly, when I ask this question on reddit, asking about the risks of inefficiencies and the lack of coordination, most replies indicate that this is a good thing, claiming that it helps to boost capabilities, although most skip replying the part of my question where I asked about the areas of inefficiencies and fiscal wastage from overlapping jurisdiction.

In any case, it is probably that most things boil down to both politics and the availability of money. After World War 2, during the formation of the National Security Act of the 1947, there were calls to abolish the Marines, while on the aviation side, there was a similar tussle between the poto-USAF and USN aviation over the role of land-based naval aviation. Even after the NSA 1947, the so-called “Key West Agreement” was the result of the USAF and US army compromising over what the USAF seen as the US Army intruding into its domain.

I would appreciate any hindsights that fellow forummers here share. Pls feel free to post your comments and thoughts in this thread.

In Part 2, I will see how such overlapping domains tended to be viewed as "coup proofing" in non-western autocracies.

For Part 3, I will look into the role of Non-Western Marine forces in Asia-Pacific countries, and in particular, I will look into the political impetus that underpin their creation – and the factors that enable their continued existence of the following branches:

References and Citations

  1. Inventory of SAMs of Soviet Air Defence Forces: Soviet Air Defence Forces - Wikipedia
  2. Soviet Air Defence Forces Fighter Fleet: Soviet Air Defence Forces - Wikipedia
  3. Indian Naval Air Arm: Indian Naval Air Arm - Wikipedia
  4. Japanese Navy Fleet Air Force (JMSDF): Fleet Air Force (JMSDF) - Wikipedia
  5. UK Royal Navy Fleet Air Arm: Fleet Air Arm - Wikipedia
  6. Spanish Naval Air Arm: Spanish Navy - Wikipedia
  7. Italian Navy Aviation: Italian Navy Aviation - Wikipedia
  8. Israel Navy Aircraft: Israeli Navy - Wikipedia
  9. US Army Aircraft Inventory: List of active United States military aircraft - Wikipedia
  10. Slaying the Unicorn: The Army and Fixed-Wing Attack: Slaying the Unicorn: The Army and Fixed-Wing Attack - War on the Rocks
  11. Marine Fighter Attack Squadrons: List of active United States Marine Corps aircraft squadrons - Wikipedia
  12. F-4 Phantom operated by USMC: United States Marine Corps Aviation - Wikipedia
  13. F-18 Operation by USMC: United States Marine Corps Aviation - Wikipedia
  14. USMC F-4 Phantom VMFA-323 Air Wing on USS Coral Sea: VMFA-323 - Wikipedia
  15. USMC F-18 Phantom VMFA-314 Air Wing on USS Coral Sea : VMFA-314 - Wikipedia
  16. Semper Fidelis: Defending the Marine Corps: Semper Fidelis: Defending the Marine Corps
  17. How the US Navy retained control over land-based naval viation: How the Air Force Got Its Start 72 Years Ago
  18. Marine Corps University > Research > Marine Corps History Division > Frequently Requested Topics > Historical Documents, Orders and Speeches > The National Security Act of 1947
  19. “Treaty” between US Army and USAF: This was the Army and Air Force 'treaty' on aircraft - We Are The Mighty


At least within the US armed forces, this supposed 'overlap' in capabilities is often due either to the perception/opinion of a capability developing armed service not receiving the desired capabilities from another service, or at least receiving them to the degree desired. The US Army's desires and requirements for CAS, ground attack, and tactical/battlefield transport/airlift vs. what the USAF can and will provide being excellent examples. At the same time, the fate of the C-27J Spartan in the US armed forces is an example of some of the political fights which can break out between rival services.


Active Member
I think the US DOD overlaps are not as overlord as it might seem.
The US Army and USAF for example. The USAF forces on transports and Fast jet fixed wing. The US Army fleet is rotary wing with very limited fixed wing. Most of the overlaps are either in Business jet class or in the case of the USAF rotary wing they are small yet focused on CSAR.
or in mission sets where the USAFoperates one battle management system well the Army does another. The most overlap is in the drone fleets. Grey eagle vs Reapers.
In the Navy and Marines the two don’t so much overlap as integrate. Both aviation wings are strongly tied together. In some areas the Navy will be more strongly favored than others but Marine fighters deck on CVN just as often as Naval Helicopters on LHA. The two services are about as intertwined as you can get. This said they each have some aspects that are unique to them.
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Well-Known Member
Overlaps can either result from doctrine of capability sharing, or technological advancements. Today they're a solid combination of both.

Example of the former: A country capable of financing 1,000 fixed wing aircraft dividing them between air force, navy, and marines, for a variety of mission types.

Example of the latter: Artillery units using howitzers, drones, and missiles, to locate and destroy aerial targets with conventional munitions.

Back in, say, WW2, we still looked at pieces of hardware as very fixed in their role, and distinct from other systems.
A plane was a plane - it could have several mission types, and for every mission there was a distinct plane type.
Anti air guns were just that.
Tanks were tanks.

Technology limited these weapon types to a narrow set of missions.

Today we have air defense units capable of ground attack, and maneuvering assets capable of air defense.
With networking, big data, and big processing, every conventional asset transforms into a generic tool, and every hostile entity becomes a generic target. And as we further advance, they both become more generic until we'll eventually reach a point where any asset can attack any target with the same ease, regardless of the asset or target type.

An IFV's 30mm gun is obviously ineffective today against fixed wing aircraft. But if you put an aircraft on the ground, and an IFV right next to it, the IFV would shred it to pieces in seconds.
So how do we bring that firepower to the target? We give the IFV a real time knowledge of the target's location, and the independent computational power and algorithms to fire on that target, which is no longer transparent to it.

Battlegroups today need to be truly multi-domain in their capabilities, and it means horizontal and vertical combat, in all aspects. So a ground element will need an aerial one. And any aerial element will surely be greatly enhanced by ground support.

We can already put many assets in tiers, which in higher or lower tiers overlap with formerly totally distinct assets. For example, a low tier aircraft, like a small drone, has capability overlaps with ground ISR assets.

We will eventually reach a point where we're either keeping navy, AF, ground etc as formal branches for the sake of logistics or organization of training, or going full on regional commands being tomorrow's pseudo-branches.
Every regional command will be broken down to theaters to which a solution will be tailored, with the assets also region-tailored.

We've seen plans for the future 6th gen fighter from the US, the PCA, being divided into regional categories, with two versions planned not for services but for specific regions. E.g an Atlantic PCA.
How long until we see the DLP (Decisive Lethality Platform - Abrams replacement) in variants like DLP-arctic, DLP-SEA, DLP-EU?


The Bunker Group
Verified Defense Pro
Interestingly, many large navies that have its own fleet of fixed wing aircraft, also tend to have its own aviation branch, examples include India, Japan, UK, Spain, Italy.
Since Italy is mentioned, as a historical overview:
  • The air components of Army and Navy were integrated into the Air Force in 1937. These formed separate commands within the Air Force that were nominally placed under OPCOM of the respective force they supported. The lack of coordination resulting from this transfer proved fatally wrong on multiple occasions in WW2 (i.e. the Air Force not making the relevant Air Wing available when and where the Navy needed it), but was continued nonetheless.
  • Postwar there was an actual fight over responsibilities when the Navy, planning to buy an aircraft carrier, started buying its own aircraft and having pilots trained in the 1950s. The Air Force based on the 1937 law confiscated the aircraft, and the aircraft carrier plans were abandoned.
  • In 1956 a change of law permitted other forces to field aircraft below 1,500 kg MTOW. Outside some trainer aircraft this changed little though, the Air Force continued to provide all fixed-wing aviation for all forces. They didn't really care about helicopters, so Army and Navy started fielding those normally.
  • In the 70s the Navy tried again, building the light carrier Guiseppe Garibaldi. Due to the legal situation the carrier was initially only operated as a helicopter carrier. In 1989 the Navy - having successfully introduced the nominal capacity - finally successfully lobbied the right people to have laws changed, allowing them to buy combat aircraft (Harriers) for the carrier. Notably this remains limited to carrier combat aircraft. Maritime Patrol Aircraft continue to be owned by the Air Force (41st Air Wing, 88th ASW Squadron) and placed under OPCOM of the Navy.