Military Strategy Magazine  /  Volume 8, Issue 1  /  

Flexible Response and Integrated Deterrence at Sea in the 21st Century: Implications for the U.S. Navy

Flexible Response and Integrated Deterrence at Sea in the 21st Century: Implications for the U.S. Navy Flexible Response and Integrated Deterrence at Sea in the 21st Century: Implications for the U.S. Navy
USS Gerald R. Ford, US Navy, Public Domain
To cite this article: Russell, James A., “Flexible Response and Integrated Deterrence at Sea in the 21st Century: Implications for the U.S. Navy,” Military Strategy Magazine, Volume 8, Issue 1, summer 2022, pages 20-26.
Disclaimer: The author is an associate professor in the Department of National Security Affairs at the Naval Postgraduate School in Monterey, California. The opinions presented here are the those of the author alone.

Is there a relationship between what senior U.S. officials today call “integrated deterrence” with Western strategy from an earlier era known as Flexible Response developed by NATO in 1967 to address the military threat posed by the Soviet Union and Warsaw Treaty Organization to Western Europe? There is a distinctive intellectual genealogy between these terms, which require strategists and policy makers to examine the implications for 21st century maritime strategy and naval power.[i]

Deterrence is Back…

Deterrence is back as a United States (and U.S. Navy) strategic priority – referred to in the current context as something called “integrated deterrence.” According to U.S. Defense Secretary Lloyd Austin: “…integrated deterrence means using every military and non-military tool in our toolbox, in lock-step with our allies and partners. Integrated deterrence is about using existing capabilities, and building new ones, and deploying them all in new and networked ways… all tailored to a region’s security landscape, and in growing partnership with our friends.”[ii] In separate remarks, Undersecretary of Defense (Policy) Colin Kahl, has emphasized the following additional elements of the integrated deterrence concept: (1) the integration of military and non-military instruments across governments; (2) making critical infrastructures more resilient in the face of disruptive attacks – attacks meant to slow coming to the aid of US allies; (3) deny the enemy the ability to realize short, fait accompli type scenario attacks on key allies.[iii]

In April 2021, Austin emphasized that “the cornerstone of America’s defense is still deterrence, ensuring that our adversaries understand the folly of outright conflict.”[iv] Austin called for “the right mix of operational concepts and capabilities—all woven together and networked in a way that is so credible, flexible, and formidable that it will give any adversary pause.”[v] This integration, as noted by Austin, must occur across the domains of conflict: land, sea, air, cyber, and space—knocking down barriers to organizational cooperation along the way. Austin emphasized that integrated deterrence also must be based on four additional elements:

  • Must exist across platforms and systems that are not stove-piped; and which do not depend on a single service.
  • Ensuring that capabilities like the global positioning system can continue even if it is attacked with missiles, cyber tools, or space-based weapons.
  • Employing cyber effects in one location to respond to a maritime security incident hundreds of miles away.[vi]
  • Integrating networks with U.S. allies and partner nations.[vii]

The Navy faces a number of challenges as it seeks to reacquaint itself with concepts like deterrence, escalation dominance, and the complex relationship between weapons across warfare domains. Although these concepts and relationships were used extensively to guide strategy during the last century, today they must be applied to new challenges, new technologies, and wholly different political settings than the ones that animated peer competition during the Cold War. In short, the Navy needs an intellectual revolution as much as it needs different planning mechanisms, war fighting concepts, new weapons, and different platforms as it searches for ways to address the multifaceted challenges of deterrence and warfighting across the global commons. To move forward, the Navy should examine its experiences from 60-odd years ago to help the institution build momentum for an intellectual revolution to address current challenges.

Back To Basics

What is deterrence, exactly? In their landmark book Deterrence in American Foreign Policy: Theory and Practice, Alexander George and Richard Smoke offered up the general proposition that remains valid: “In its most general form, deterrence is simply the persuasion of one’s opponent that the costs and/or risks of a given course of action he might take outweigh the benefits.” [viii] Hence, the objective of deterrence is to shape the decision making of a particular state to reduce the incentives for that state to act, and/or use force to achieve political objectives. The end result of deterrence is that no action is taken—most particularly the use of force. The concept of deterrence has been a centerpiece of U.S. strategy and defense policy in the post-World War II era that gathered momentum with the advent and spread of nuclear weapons.[ix] As an intellectual construct, the intuitive appeal of deterrence was and remains obvious, particularly as the nuclear states operationalized the capacity to build and field thermonuclear fusion weapons—the use of which would have ensured destruction on a scale that could scarcely be imagined. After all, what state would seek to start such a war, the costs of which could entail the destruction of significant portions of humanity, including the state that initiated the war?

As noted by George and Smoke, navies have historically played a strong role in deterrent strategies in which the deployment of naval forces to trouble spots became a ritualized response to a crisis in which the size of the squadron/force deployed to the trouble spot became regarded as an index of the commitment of the deploying power.[x] Thus, these deployments became instrumental in the political signaling process upon which deterrence also rests, since the actors involved in the deterrence bargaining framework must also perceive that the threat to act is credible.[xi]

Scholars subsequently modified these basic concepts of deterrence, segregating deterrence strategies into two approaches: (1) deterrence by denial; (2) deterrence by punishment.

Deterrence by denial seeks to make it extremely difficult if not impossible for a foe to achieve their objectives through the use of force. The foe, in this case, would thus perceive that the costs of action would be too high to justify the use of force.

Deterrence by punishment threatens a foe with a series of potential consequences across a wide spectrum of military and political actions that can include escalation to nuclear weapons, political steps such as sanctions, and other political steps to raise the costs of action to a foe contemplating using force.[xii]

Other strands of the deterrence literature address adversary calculations in circumstances short of nuclear war. Indeed, there is rich literature on conventional deterrence,[xiii] which is a closely related cousin to nuclear deterrence literature. In the post-Cold-War era, scholars created yet another strand of this literature called cross domain deterrence that applied deterrence concepts to changed strategic and military circumstances. In the modern era, advanced militaries conceptualize military operations across various domains: land, space, cyber, maritime surface and subsurface, and in the skies. These operations, it is thought, potentially blur the Cold War-era distinctions between the levels of war: strategic, operational, and tactical that once were defined at the strategic level by nuclear weapons. Added to this mix must be digitized and proliferating weapons technologies that have increased accuracy and destructive power that can be delivered at ever greater distances. A fundamental idea in this literature is that it is possible to affect adversary behavior by threatening action in one domain to deter potential use by an adversary in another domain.[xiv]

Flexible Response and the Navy

What does all this have to do with the Navy and Flexible Response? Historically, the Navy is no stranger to deterrence. During the Cold War, the U.S. Navy provided a vital part of the nation’s nuclear deterrent through the eventual deployment of ballistic missiles in the Polaris class nuclear-powered submarines. These platforms were invulnerable to attack, thereby preserving the nation’s second-strike capability and stabilizing the nuclear balance of terror.[xv] In addition, the U.S. Navy played an instrumental role in operationalizing the doctrine of Flexible Response on the high seas. If required, the Navy could draw upon nuclear bombs, shells fired from large caliber guns, depth charges, anti-submarine torpedoes and rockets, surface to air missiles, and sea-launched cruise missiles to preserve escalation dominance over its Soviet foe. During the Cold War, approximately 20 percent of America’s nuclear arsenal was at sea on an annual basis.[xvi] The Navy deployed its nuclear arsenal in the Atlantic, Pacific, and Mediterranean until President George H. Bush ordered these weapons removed from Navy ships in 1991.

Conceptually, Flexible Response posited a direct relationship between nuclear and conventional weapons knitted together as a “seamless web.” That seamless web consisted of conventional weapons, short range tactical nuclear weapons (first deployed to Europe in 1953) all the way up to and including strategic nuclear missiles based in the United States and Europe. These weapons fit within an alliance framework that sought to build up and deploy conventional forces along the inter-German border to protect Europe from a Soviet invasion. In 1956, the alliance agreed on massive retaliation as its strategy in NATO military document MC 14/2,[xvii] thereby linking the conventional and nuclear components in an integrated allied military strategy built on the deterrent value of nuclear weapons. The initial idea was to hold the Soviet advance long enough and as far forward as possible until nuclear retaliation, becoming known as the “tripwire” strategy. Flexible response evolved out of these circumstances and a robust debate at the time about limited war, reflecting a general unease with reliance on massive retaliation and the prospect of armed confrontations in places where it was unclear what role, if any, could be played by nuclear weapons.

In the early 1980s and under the leadership of Navy Secretary John Lehman, the Navy asserted its direct warfighting role against the Soviet Union with the Maritime Strategy that focused on defending alliance supply lines across the Atlantic Ocean, bottling up the Soviet northern fleet along the GIUK gap, and undertaking land- and sea-based operations against the Soviets on the Kola Peninsula. While NATO always remained lukewarm to these ideas, the maritime strategy became an important raison d’etre for the United States Navy in carving out a discrete and concrete Cold War-era war-fighting mission that had powerful nuclear and conventional components.[xviii]

In retrospect, the 1980s represented a high-water mark for the U.S. Navy in terms of connecting the service to a war that, at its height, could have included nuclear weapons launched from its ships, aircraft, and submarines across a spectrum of conflict. After the end of the Cold War, however, the Navy’s connection to U.S. defense strategy languished as attention shifted to various regional crises across the Middle East and South Asia, which culminated in the land wars in Iraq and Afghanistan following the 9/11 attacks.

With the removal of a principal adversary on the high seas, navies have not been the primary weapon of developed states. Instead, the developed states turned their focus to policing or nation building operations on land in places like Iraq, Afghanistan, and the Sahel as well as coping with the disintegration of states like Libya, Syria, and Yemen. Global navies, including that of the United States, have continued to focus on areas outside of high-intensity wars with such activities as counterpiracy, disaster relief, disrupting the trade in illegal drugs, and rescuing refugees. While the U.S. Navy has participated in various strike operations in the Persian Gulf and Afghanistan, its tasks in or related to war on the high seas have become obscured simply because the high seas thankfully have been free of large-scale political violence. With this retreat from warfighting missions has also come a retreat from important strategic concepts such as deterrence.

Yesterday, All My Troubles Seemed So Far Away…

The bygone era of Flexible Response is, well, bygone. From the Navy’s perspective, what are the similarities and differences between integrated deterrence and flexible response? While both ideas appear in strikingly different strategic circumstances of near-peer competition, there are important strands of continuity between these ideas. Flexible Response appeared as a backlash to the Eisenhower administration’s doctrine of Massive Retaliation. Some argued that this doctrine reduced America’s flexibility in dealing with situations short of all out nuclear war.[xix] The United States needed to address Soviet and/or communist adversaries short of this unlikely circumstance, as spelled out in Maxwell Taylor’s book The Uncertain Trumpet (New York: Harper and Row, 1960). President Kennedy agreed with this perspective and emphasized war-fighting capabilities across the spectrum of combat.

Today’s emphasis on integrated deterrence arise due to a perceived shortfall in the ability of the United States to address “grey zone” or so-called hybrid war in which adversaries are drawing upon military or paramilitary instruments in situations short of all-out war to achieve political objectives. China’s “grey zone” tactics across the South China Sea is one example of this phenomenon, in which so-called Chinese fishing vessels and coast guard ships are being used as political instruments to push dubious territorial claims in places like the Scarborough Shoals and elsewhere.

A second important similarity between these approaches is their shared recognition that multi-domain operations are a characteristic of the battlefield and an object of deterrence strategy. Both approaches envision deterrence functioning across battlefield wartime domains. Flexible Response envisioned a “seamless web” of combat integration meant to present an imposing mix of capabilities to deter the opponent and, if necessary, control escalation in conflict by having the ability to trump the opponent’s response at any level. Flexible Response clearly linked conventional and nuclear weapons, envisioning the use of nuclear weapons across a range of tactical scenarios. During the era, America’s forces were equipped with various types of tactical nuclear weapons that formed part of an escalation sequence that included intermediate- and intercontinental range nuclear missiles.[xx] In the escalatory sequence, nuclear weapons served as the vital escalation firebreak in which there was a clear political and military difference between conventional and nuclear weapons on the escalation ladder.

Bearing these similarities in mind, there also are important differences between Flexible Response and integrated deterrence. At the top of the list must be the 21st century’s changed geopolitics. Integrated deterrence clearly is directed at China and, to a lesser extent, Russia, on the Eurasian land mass. Unlike the era of Flexible Response where NATO sought to protect its member state territories from invasion, the objectives of integrated deterrence are less well defined. All that really can be said is that the Indo-Pacific constitutes a vast maritime domain that make navies a principal feature of any deterrence framework. In addition, the political circumstances present in Europe that undergirded Flexible Response are absent in the Indo-Pacific. Other than the Indo-Pacific’s loosely configured Quadrilateral Security Dialogue comprised of the United States, Australia, Japan, and India, there is no collective defense organization in existence. Persistent fractious regional relations prevent the development of a unified threat perception to drive collective planning to develop shared understandings of strategic problems.

There are other important differences. While both integrated deterrence and Flexible Response envisioned a seamless deterrent web, today’s “web” is much more complex due to a wider number of weapons available for use. The nature of weapons today applied across domains for advanced militaries suggests that distinctions between escalation levels can be blurred and, in tandem, involve a more complex targeting environment available in the different warfare domains. Cyber and space operations, for example, offer up the possibility of decapitating military strikes to cripple critical command, control, communications, and intelligence nodes – thereby blinding an enemy – without kinetic physical destruction. Cyber weapons also can be used against critical civilian and military infrastructure. In some respects, this aspect of multi domain operations returns us to debates of the 1950s about mutual and myriad vulnerability points between adversaries in what was then called the balance of terror. During the 1950s, Albert Wohlstetter analyzed the vulnerability of the Strategic Air Command’s 16 bases and its small number of nuclear weapons storage depots. He concluded that these vulnerable targets created incentives for pre-emptive strikes – incentives that inherently destabilized the balance of terror.[xxi] Such a calculus clearly remains relevant on today’s battlefields in which multiple targeting vulnerabilities are as problematic today as they were when Wohlstetter grappled with these issues 60 years ago.

Changing weapons technologies constitute another source of escalation instability in cross-domain operations. The preceding discussion of cyber weapons illustrates a central point: 21st century non-nuclear weapons have the potential to be used individually and in combination in ways that can blur the distinctions between the strategic, operational, and tactical levels of war. Moreover, states like Russia also have fielded a new generation of lower yield tactical nuclear weapons that are intended for battlefield use.[xxii] These weapons further erode the distinction between conventional and nuclear weapons and the implied escalation ladder based on the destructive power of nuclear weapons.

Moreover, the accuracy, destructive power, and ever-increasing ranges of weapons give actors the ability to disable strategic level enemy targets. Hypersonic missiles boast the capability to hold a wide range of targets at risk with limited warning time that also pose great difficulties for missile defense systems. These weapons also raise difficulties for those on the receiving end, due to the possibilities that these weapons could carry a nuclear payload. Such a scenario raises the specter of launch on warning uncertainties for the state being attacked, presenting a profound escalation risk in war.

Lastly, the U.S. Navy must confront the wider impact that integrated deterrence and cross domain operations could have on wartime operations at sea.[xxiii] Any form of deterrence depends on the credibility of the actor seeking to deter its adversary. As previously noted, actor credibility is a function not only of political commitment but of military capability. To preserve credibility, the Navy will need to equip and train itself for cross-domain operations that may render traditional ideas of a war at sea irrelevant. A 21st century war at sea almost certainly will look dramatically different than the kind of war envisioned during the Cold War and the force structure that evolved out of World War II.

During World War II and the Cold War, the Navy sought to control the oceans for the purpose of conducting strike operations ashore and, in combination, to move land forces to and from the war while keeping those forces re-supplied. The Navy postured itself to fight across the three distinct maritime domains: surface, subsurface, and in the air. The aircraft carrier served as the central platform for power projection, with its airplanes used for strike operations on land and at sea. Cold War-era battles at sea were envisaged as a variation on the Navy’s experiences in the Pacific during World War II. Today, however, aircraft carriers and their supporting fleets have lost their unrestricted maneuver space off enemy shores and are out-ranged by a variety of accurate, shore-based missile systems as embodied in China’s DF-series of anti-ship missiles. It is unlikely that a 21st century naval war in the Indo-Pacific will involve a re-enactment of the Leyte Gulf – the largest naval battle of World War II.

Instead, 21st century cross domain operations may see the Navy become more of an enabler of operations and capabilities rather than the principal instrument responsible for prosecuting them. Sea control and power projection may look dramatically different in a multi- and cross-domain war. Surface fleets will almost certainly need more autonomous systems drawing upon artificial intelligence to enable ongoing reloads of kinetically based weapons across various domains. Instead of delivering strike operations on land, carrier air wings may be used to provide route security for autonomous systems delivering long-range payloads on a wide-ranging maritime battlefield.


This analysis concludes that Flexible Response provides a sound point of departure for the Navy to think through the implications of integrated deterrence and the multi-domain concept of operations that operationalizes integrated deterrence. Flexible Response envisaged a seamless web of conventional and nuclear capabilities knitted together by an escalation ladder that sought to convince the opponent against taking action. Integrated deterrence presents a variation on the basic premises of Flexible Response, but adds multiple layers of complexity across different warfare domains with newer weapons technologies that address the 21st century’s changed political and strategic circumstances.

The Navy faces significant challenges in adjusting to integrated deterrence. The Navy today is the least joint of all the US military services, yet the requirements of integrated deterrence require a greater degree of “jointness” than ever before. Moreover, integrated deterrence also calls for changes in the way the service organizes, equips, and trains itself to support a multi-domain war. Yet here again, the lessons from the era of Flexible Response could prove instructive. The 1960s saw the Navy introduce new families of weapons aboard ships and submarines and integrated itself into national-level command plans for nuclear operations. The Navy took these dramatic steps in the 1960s and could do so again today.

In an earlier era, the Navy embraced the requirements of Flexible Response – equipping and training the fleet with new weapons for a wide range of wartime scenarios. We are just at the beginning of fleshing out concepts like integrated deterrence and determining what it may mean for force structure and operations. The suggestion in this essay is that it calls for nothing less than an intellectual revolution to conceptualize integrated deterrence and, in tandem, operationalize the ideas with plans, policies and programs. That revolution must start – the sooner the better.


[i] Also see Michael Clarke, “Back to the Future: Is ‘Integrated Deterrence’ the New ‘Flexible Response’?, The National Interest, October 23, 2021; Michael O’Hanlon,
[ii] Secretary of Defense Remarks at the 40th International Institute for Strategic Studies Fullerton Lecture (As Prepared), July 27, 2021, Singapore.
[iii] Jim Garamone, “Concept of Integrated Deterrence Will Be Key to National Defense Strategy, DOD Official Says,” DOD News, December 8, 2021.
[iv] “Secretary of Defense Remarks for the INDOPACOM Change of Command,” Department of Defense, April 30, 2021,
[v] Department of Defense, “Secretary of Defense Remarks.”
[vi] Department of Defense, “Secretary of Defense Remarks.”
[vii] Department of Defense, “Secretary of Defense Remarks.”
[viii] Alexander L. George and Richard Smoke, Deterrence in American Foreign Policy: Theory and Practice (New York: Columbia University Press, 1974), 1.
[ix] As chronicled in Bernard Brodie, Strategy in the Missile Age (Princeton, NJ, Princeton University Press, 1959).
[x] George and Smoke, Deterrence in American Foreign Policy.
[xi] Ibid.
[xii] Summaries drawn from Michael Mazar, “Understanding Deterrence,” Perspective Series (Rand Corp: Santa Monica, CA: 2018). Also see Glenn H. Snyder, Deterrence by Denial and Punishment (Princeton, NJ, Center of International Studies, January 1959)
[xiii] John Mearsheimer, Conventional Deterrence (Ithaca, NY: Cornell University Press, 1983). Also see James J. Wirtz, “How Does Nuclear Deterrence Differ from Conventional Deterrence,” Strategic Studies Quarterly 12, no. 4 (Winter 2018): 58–75,
[xiv] See literature review in Tim Sweijs and Samuel Zilinzik, “The Essence of Cross Domain Deterrence,” in Frans Osinga and Tim Sweijs, eds., Deterrence in the 21st Century Insights from Theory and Practice (The Hague and Berlin, Springer and Asser, 2020)
[xv] Herman Kahn, The Nature and Feasibility of War and Deterrence, P-1888-RC, 2nd printing (Santa Monica, CA: Rand Corporation, 1960),; Albert Wohlstetter, The Delicate Balance of Terror, P-1472 (Santa Monica, CA: Rand Corporation, 1958),
[xvi] Robert S. Norris and Hans M. Kristensen, “Declassified: U.S. Nuclear Weapons at Sea During the Cold War,” Bulletin of Atomic Scientists 72, no. 1 (2016): 58–61,
[xvii] History drawn from J. Michael Legge, Theater Nuclear Weapons and the NATO Strategy of Flexible Response, R2964FF (Santi Monica, CA: Rand Corporation, 1983); Gregory W. Pedlow, ed., NATO Strategy Documents, 1949–1969 (Brussels: Supreme Headquarters Allied Powers Europe, 1997),
[xviii] As covered in George Baer, One Hundred Years of Sea Power (Palo Alto: Stanford University Press, 1994).
[xix] As emphasized by Michael O’Hanlon, “The Best Defense? An Alternative to All-Out War or Nothing,” Brookings Blog, Order from Chaos, May 21, 2021, published online at
[xx] Andrew Bacevich, The Pentomic Era: The U.S. Army Between Korea and Vietnam (Washington, DC: National Defense University Press, 1986); Brian Linn, Elvis’s Army: Cold War GI’s and the Atomic Battlefield (Cambridge, MA: Harvard University Press, 2016).
[xxi] Outlines of the debate captured in Mark Trachtenberg, “Strategic Thought in America, 1952-1966,” American Political Science Review Vol. 104, No. 2 (Summer 1989) 301:334.
[xxii] For example, see William J. Broad, “The Smaller Bombs That Could Turn Ukraine into a Nuclear Battlefield,” New York Times, March 21, 2022.
[xxiii] Concepts emerged several years ago under the rubric of the Air Sea Battle. The next iteration was addressed in Michael E. Hutchens, William D. Dries, Jason C. Perdew, Vincent D. Bryant, and Kerry E. Moores, “Joint Concept for Access and Maneuver in the Global Commons: A New Joint Operational Concept,” Joint Forces Quarterly 84 (1st Quarter 2017) 134:139; Kenneth J. Braithwaite, Secretary of the Navy, Advantage at Sea: Prevailing with Integrated All Domain Naval Power (Department of Navy, Washington, DC: December 2020).