Combined Arms Support to Submarine Operations

Last month in the conclusion to my series examining the Jeune École, I noted that Germany’s use of submarines in the Atlantic for theater denial and Guerre de Course during the two World Wars—while incredibly costly to the Allies in terms of blood and treasure—ultimately failed in large part because German surface combatants and land-based aircraft could not seriously offset Allied anti-submarine efforts.

German U-boats were on their own in the Atlantic during the First World War because their surface combatant brethren could not break through the Royal Navy’s North Sea blockade in numbers. Granted, a handful of German large and medium surface combatants were forward deployed when the war broke out, and a few Germany-based medium surface combatants and armed auxiliaries managed to access the Atlantic at various points over the war’s course. All of these warships, though, operated as commerce-raiders either by design or by default—and few managed to operate for longer than a handful of months before being neutralized. Allied anti-submarine forces, whether operating independently or (after April 1917) as convoy escorts, therefore only had to contend with their prey

Nor did U-boats receive substantive support from the Kriegsmarine’s surface forces during the Second World War. If anything, Germany was at an even steeper surface order of battle deficit relative to the Royal Navy than had been the case two decades earlier. As a result, and with the exception of the April-June 1940 Norwegian campaign, the Kriegsmarine once again principally used its larger surface combatants for commerce-raiding. Although the Kriegsmarine’s surface threat to Britain’s lines of communication with the Americas was peacemeal and limited to 1939-1941, the threat it posed to the allies’ lines to the Soviet Union through the Norwegian Sea was more serious and lasted until 1943. One could make the case that the Kriegsmarine’s large surface combatants based in Norway supported U-boats in the case of convoy PQ-17, but that stemmed from the British Admiralty erroneously ordering the convoy’s ships to scatter to their fates in the belief that German surface raiders including the Tirpitz were approaching (they were not). In any case, the sad story of PQ-17 was not repeated.

The advent of theater-range aircraft during the interwar years, however, meant that U-boats did receive some combined arms support. Specialized Luftwaffe bombers were fielded to provide surveillance and reconnaissance support to Kriegsmarine surface and submarine units. These bombers also conducted anti-ship raids of their own. The Luftwaffe was able to iteratively increase its oceanic reach throughout the war, established a dedicated command for maritime operations in the northeastern Atlantic, and introduced radio-controlled anti-ship weapons that permitted standoff attacks. The first combat use of one of these weapons, in fact, caused the allies to temporarily halt offensive anti-submarine Surface Action Group (SAG) operations in the Bay of Biscay; this provided U-boats based on the French Atlantic coast with a temporary window of opportunity for safer transits to and from the open ocean.

And yet, the Luftwaffe never operated enough aircraft to pose a persistent threat to allied convoys or offensive anti-submarine SAGs. Moreover, the Luftwaffe and Kriegsmarine never hammered out doctrine, communications protocols, or planning processes that could enable effective operational coordination. On-scene tactical coordination between aircraft and U-boats was sporadic; the occasional noteworthy successes that did occur did not translate into major campaign gains. Luftwaffe land-attack raids against major British ports, naval bases, and shipbuilding hubs to suppress convoy and SAG operations as well as new ship construction were sustained for only the first half of 1941, were largely ineffective in their operational purpose, and were ultimately discontinued. Most significantly, U-boats operating in the western and southern Atlantic were outside the Luftwaffe’s range—and thus were on their own.

The Soviet Union’s leading maritime strategist of the Cold War, Fleet Admiral Sergei Gorshkov, took note of all this. In his 1976 book The Sea Power of the State, Gorshkov observed that Germany’s Second World War U-boat operations ultimately failed to achieve their strategic objectives in part because they

“…did not have the support of other forces, notably, aircraft, which could have been an irreplaceable means of reconnaissance, to fulfill the tasks of destroying anti-submarine forces and also to act against the economy of the opponent, particularly his shipbuilding industry, and to inflict blows on cargo ships in the ocean.” (Pg 120)

Gorshkov then observed that while German U-boat operations were representative of the roles submarines should play in war, the Germans erred as

“Throughout the war not a single attempt was made to counter the anti-submarine forces of the Allies in an organized way from operating with total impunity.” (Pg 120-121)

Notwithstanding the irony that Soviet interests in the war were on the receiving end of the U-boat operations he lauded, Gorshkov appeared to be arguing that Soviet attack submarines should perform much the same roles in a notional conflict with the U.S. and NATO. He further seemed to argue that Soviet air forces should provide his submarines with the direct and indirect forms of support that he had outlined.

Whatever Gorshkov may have actually believed, his Navy’s planned use of submarines for barrier protection of the Soviet maritime periphery represented the polar opposite of what his book seemed to recommend. Part of this was due to the paramount Soviet military-strategic task of protecting the motherland from naval strikes, whether conventional or nuclear. Part of this was also due to Soviet leaders’ fears that their strategic nuclear reserve force—their SSBNs—might be subjected to wartime attrition via U.S. and NATO conventional offensive anti-submarine operations. If the U.S. and NATO could attain a superior ‘correlation of nuclear forces’ during the conventional fight, Soviet logic went, then the West would gain a major card to play in the bargaining over war termination. Soviet Naval Aviation, surface forces, and attack submarines were consequently tasked with preventing U.S. and NATO naval forces from attacking the SSBNs; comparatively few Soviet attack submarines were to be hurled at NATO’s trans-Atlantic lines of communication at the beginning of a war.

It follows that offensive strategic anti-submarine warfare was one of the primary reasons the 1980s U.S. Maritime Strategy emphasized forward operations within the Soviet oceanic periphery. The strategy suggested that if U.S. carrier battleforces in the Norwegian Sea and Northwest Pacific could weather or outright defeat Soviet anti-carrier forces’ onslaught early in a war, then U.S. and allied anti-submarine forces might gain more operational freedom to interdict older Soviet SSBNs (or any Soviet SSNs for that matter) attempting to break out through forward geographic chokepoints into the ‘world ocean.’ Moreover, U.S. naval airpower could also be theoretically used to suppress Soviet surface and airborne anti-submarine forces protecting the newer Soviet SSBNs’ bastion patrol boxes. If these Soviet anti-submarine forces could be suppressed, then U.S. and NATO SSNs operating against the bastions (or conducting land-attack cruise missile strikes into the Soviet Union, if so ordered) would only face opposition from their acoustically-inferior Soviet counterparts. In essence, the 1980s Maritime Strategy redirected Gorshkov’s logic regarding combined arms support of submarine operations against his own fleet.

The late Cold War is not the only example of U.S. combined arms support of submarine operations. Again, as I noted in my Jeune École series’ finale, U.S. offensive submarine operations against Japanese sea lines of communication during the Second World War benefitted indirectly from the Imperial Japanese Navy’s myopic fixation on fleet-on-fleet operations:

The U.S. Navy fast carrier task force’s advance across the Pacific arguably provided increasing amounts of indirect combined arms support to their submariner brethren over time by occupying the attention of Japanese naval resources that theoretically could have been assigned to convoy defenses or submarine-hunting groups. Although the Imperial Japanese Navy showed little interest in protecting convoys from submarines during the war, an absence of the U.S. Navy carrier threat in the Central Pacific after 1942 might have provided room for reallocating some Japanese fleet assets to anti-submarine tasks as Japanese merchant vessel losses mounted.

So what might these history lessons mean for future U.S. Navy doctrine and operating concepts?

For starters, it’s important to keep in mind that a submarine’s combat “invisibility” has never been absolute. If a submarine torpedoes a ship, then the other side’s anti-submarine forces gain a “flaming datum” to orient their search. If a submarine launches a missile or raises a periscope/ESM mast for too long within the other side’s effective radar (or visual) coverage and is detected, then the other side's hunters know precisely where to start their cordon and redetection efforts—or place quick-response weapons in the water. A submarine may be able to scan or shoot far enough away from an opponent’s anti-submarine aircraft or surface combatants to be able to “break datum” before the hunters can react effectively, but it cannot count on that favorable scenario always being available. And the closer a submarine operates to an adversary’s coast, the denser the coverage by the adversary’s anti-submarine sensors (whether seabed-mounted sonar arrays, ship and aircraft-mounted sonars/radars, or fishermen’s eyes) and platforms will be. These assets might not be able to find or shoot at the submarine, but their presence might unnecessarily complicate its mission. In some situations it might even delay or prevent the submarine from completing that mission.

In a major modern war, U.S. SSNs and SSGNs would be tasked with land-attack strikes, special forces insertion/extraction, and intelligence/surveillance/reconnaissance collection within a contested zone’s inner reaches. The SSNs would additionally be tasked with forward anti-submarine and anti-surface operations. Just as was the case in the 1980s Maritime Strategy, our submarines might situationally benefit from some external help from other U.S. or allied forces in suppressing the adversary’s ability to conduct effective anti-submarine operations.

This help might take the form of aircraft performing anti-ship missile raids against enemy anti-submarine SAGs inside a contested zone. It might take the form of offensive sweeps by fighters against the adversary’s maritime patrol aircraft. The mere fact that adversary anti-submarine forces were attacked in a particular area in a particular way might induce the adversary to limit or cease operations in that area while it figures out how to adapt; this could be exploited to great effect by U.S. submarines even if the ‘pause’ only lasted for a few days.

External forces might also provide submarines with deception and concealment support. This might consist of air or surface naval operations that have the primary or secondary purpose of distracting the adversary’s attention from a U.S. submarine’s operating area. Or perhaps air or surface forces might release submarine-simulating unmanned underwater systems at some standoff distance from the adversary’s coast; these decoys could then “swim” forward into designated areas to confuse or distract the adversary’s anti-submarine forces.

External support to forward submarine operations might additionally include surveillance and reconnaissance aircraft that report their surface pictures via interior lines of networking to a higher-echelon commander. The commander could then broadcast that information along with theater or national-level naval intelligence information “in the blind” for our submarines to receive and use for their purposes.

If authorized by U.S. political leadership, combined arms support to our submarines might even take the form of U.S. cruise missile strikes against the adversary’s naval and air bases supporting anti-submarine operations. As I’ve noted previously, it must be understood that a U.S. President’s decision-making on this question would be heavily—and perhaps decisively—affected by the escalatory precedents already set by the adversary (regardless of who that might be) in the conflict. 

These forms of external support would not be possible to all U.S. forward submarine operations due to asset availabilities. Nevertheless, air or surface operations could be sequenced or coordinated to support specifically prioritized submarine operations or operational periods.

The adversary’s ability to pose an excessively high threat to U.S./allied air or surface operations within a contested zone’s inner sections would also be a major limiting factor. Special assets such as very low observable aircraft might be needed to conduct attacks in support of submarine operations—or cue attacks by other forces armed with long-range weapons. These penetrating aircraft in turn might need to be supported via submarine-launched land-attack cruise missile strikes against an adversary’s wide-area air surveillance sensors or air defense systems. This is a great example of why mutual support between combat arms is so critical in modern warfare. Even so, it is quite likely that the further forward a submarine operates within a contested zone, the more likely external support (if any is possible) will be indirect.

None of this changes the fact that U.S. submarines will assuredly conduct high-risk independent operations deep within an adversary’s maritime periphery in a notional major war. That’s been a constant from the Second World War, through the Cold War, to today. U.S. direct and indirect support of submarine operations has also been a constant, whether it was inadvertent as in the Second World War or consciously planned for as in the 1980s Maritime Strategy. I’d argue that external combined arms support (as possible and relevant) can have much to offer our submarines in the present and future as well.

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I'll be on hiatus next week. I aim to resume posting the week of August 10th.

The views expressed herein are solely those of the author and are presented in his personal capacity. They do not reflect the official positions of Systems Planning and Analysis, and to the author’s knowledge do not reflect the policies or positions of the U.S. Department of Defense, any U.S. armed service, or any other U.S. Government agency.