Five weeks before the war against Iran began, the Pentagon published a strategy warning that the United States could find itself facing simultaneous major conflicts across several theaters. The 2026 National Defense Strategy, released on 23 January, gives the problem an unusually explicit name: simultaneity. One or more adversaries might coordinate their actions, but coordination is only part of the concern. They might also take advantage of American commitments elsewhere, creating situations in which Washington has to decide which demands deserve priority when forces, munitions, and political attention cannot be treated as freely available everywhere at once. The document goes so far as to describe the danger of the United States being drawn into simultaneous major wars across theaters as the risk of a third world war.
There is something important in the way the strategy frames the problem. It moves away from the force-planning assumption that shaped much of the 1990s, when the United States sought to maintain enough military capacity to fight two major regional wars at roughly the same time. The current strategy still calls for a larger joint force and a stronger industrial base, although its answer increasingly extends beyond simply adding more capacity. Europe is expected to assume primary responsibility for its conventional defense, regional allies are expected to carry more of the burden in the Middle East, and South Korea is expected to take primary responsibility for deterring North Korea, all with more limited American support. Simultaneity, in other words, becomes a problem of allocation as much as one of force size.
The wars in Ukraine and Iran have made that problem easier to see because decisions taken in one theater increasingly alter the conditions prevailing in another. Reports have linked Russian intelligence sharing to Iranian targeting, although the precise scope of that assistance remains difficult to establish publicly. At the same time, the Iranian-designed Shahed family remains embedded in Russia’s strike campaign even as Russia has localized production and extensively modified the Geran variants. Ukraine has itself crossed into the Iranian theater by striking an Iranian commercial vessel in the Caspian Sea and by deploying counter-drone specialists to Middle Eastern states that have faced Iranian attacks. North Korean troops, ballistic missiles, and large quantities of ammunition have meanwhile supported Russia’s war effort, reducing some of the pressure on resources Moscow would otherwise have had to supply itself.
American deployments generate similar effects. When the USS George Washington moved from the western Pacific to the Middle East in August, the immediate military balance did not change only in the theater to which it was sent. Something also changed in the theater it left, where the transfer temporarily removed a carrier presence from the western Pacific. Taiwan’s defense ministry has consequently been studying what the Iran war reveals about rapid ammunition consumption, pressure on air-defense systems, industrial mobilization, and allied cooperation. Taiwan is involved in neither war, but decisions generated by both can still alter its strategic environment.
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It is this widening network of effects that led Paul Poast to argue, first in The New York Times and subsequently in World Politics Review, that the wars in Ukraine and Iran should increasingly be understood as components of a new world war. His definition is deliberately economical. Separate international conflicts form a world war when at least two of them become interconnected and have common belligerents.
Much of the evidence behind that argument is persuasive. The wars clearly do interact, and the interactions are becoming harder to dismiss as incidental. The difficulty comes when we ask what those connections tell us about the relationship between the wars themselves. Interconnection can appear because political and military objectives are beginning to converge, but it can also emerge when separate conflicts depend on the same constrained providers. Once several governments draw on the same stocks of missiles, industrial capacity, intelligence systems, carriers, and political attention, allocating resources to one inevitably changes the possibilities available to another. The result can therefore be a system in which wars are increasingly coupled even while the political purposes for which they are being fought remain separate.
Shared scarcity across theaters
The Iran campaign has made the material side of this unusually visible. By August, the United States had expended virtually all of certain long-range precision missiles used in the campaign, close to half of its global Tomahawk stock and substantial shares of Patriot and THAAD interceptors. Those figures do not suggest that American military power has somehow been exhausted. They illustrate a more ordinary constraint. Deployable capacity is finite, and intensive consumption in one theater changes the margin available for contingencies elsewhere.
The same mechanism works in the other direction when additional capacity enters the system. North Korean manpower and materiel allow Russia to sustain parts of its Ukrainian campaign with resources supplied from outside. European support can absorb some of the burden previously carried by the United States. A carrier transferred to the Middle East strengthens one theater while reducing what is immediately present in another. Each movement creates consequences that travel beyond the conflict in which the original decision was taken. Seen this way, some of the connections between Ukraine and Iran begin to look less like evidence that the wars have merged and more like the consequences of several demands passing through the same constrained strategic infrastructure. If two conflicts depend on the same provider, movements between them can occur simply because the provider has to decide where its resources go.
Scarcity itself does not separate this configuration from an integrated war. The Allies spent much of the Second World War arguing over ships, aircraft, landing craft, industrial production, and the timing of offensives. Their military resources were constantly rationed across theaters. What made those disputes part of one war was the ability, however imperfectly, to refer them to a hierarchy of common objectives. The principle of Germany First gave that hierarchy one of its clearest expressions. Resources were divided among theaters, but their allocation ultimately served a shared political project.
Ukraine and Iran present a different arrangement. Both press on some of the same American capabilities, while the political purposes attached to those claims remain distinct. Ukraine’s war concerns territory, sovereignty, and the future security relationship with Russia. The American campaign against Iran has been publicly defined around Iranian nuclear capabilities, ballistic missiles, naval power, and support for proxy groups, while political rhetoric around the conflict has at times gone further. The same provider may therefore have to weigh both sets of claims without possessing a common political objective capable of deciding between them.
It is in that sense that the system begins to resemble a queue, although the analogy only goes so far. International politics does not distribute military capacity according to order of arrival. Ukraine is not simply waiting behind Iran. Some requests continue to be met, while others are delayed, redirected, or transferred to allies, and different capabilities can follow different priorities. Air-defence interceptors, intelligence support, naval assets, and long-range strike systems do not necessarily move according to the same hierarchy.
The states making claims on the system also have agency over their position within it. Ukraine can turn the experience accumulated against Iranian-designed drones into expertise that becomes useful to Gulf partners. European governments can provide additional capacity. South Korea can assume more responsibility for its own defense. Governments can seek alternative suppliers, bargain for priority, or take advantage of the opening created when another theater draws American resources away. Scarcity, therefore, becomes political through the way it is allocated, contested, and partly compensated for. Rationing is not simply a description of shortage. It is a form of governance under shortage.
When connection tells us less than we think
Once that possibility is admitted, interconnection becomes harder to use as a sufficient test of whether separate conflicts have become one war. Political integration can certainly generate cross-theatre effects, but shared scarcity can generate many of the same observations. Weapons move between theaters. Providers change priorities. Common belligerents appear. Decisions in one conflict affect opportunities in another. If both structures predict these effects, seeing the effects does not by itself tell us which structure produced them.
The overlap between the Korean War and the First Indochina War gives some sense of the difficulty. Between 1950 and 1953, France had combat forces in Korea while remaining deeply engaged in Indochina. China intervened directly in Korea while supplying, training, and advising the Viet Minh in Indochina. American policymakers also weighed both theaters within the same broader strategy, and a 1951 National Security Council progress report stated that military aid to Indochina enjoyed the highest priority immediately after the military effort in Korea.
The connections were therefore substantial, extending across belligerents, suppliers, and strategic priorities. Conventional historiography nevertheless continues to treat Korea and Indochina as separate wars. The example cannot settle every definition of world war, particularly because both conflicts took place in Asia and belonged to the wider Cold War confrontation. What it does show is that shared actors and cross-theatre allocation can become extensive without necessarily erasing the political distinction between conflicts.
This is why the relationship between political ends becomes important. If wars are genuinely moving towards integration, we should eventually expect that process to become visible in more than the resources sustaining them. Priorities may increasingly be decided through a common strategy. Reciprocal commitments may deepen. Governments may begin to make diplomacy in one theater conditional on developments in another. At some point, even the terms on which the conflicts can end may become connected. We can describe this as terminal integration, meaning the extent to which separate conflicts begin to share a political ending.
Terminal integration does not require a single peace treaty or a unified military command. The Seven Years War, for example, was brought to a close through the Treaty of Paris and the Peace of Hubertusburg in 1763, involving different combinations of belligerents. The wider conflict remained intelligible as one war even though its settlement was institutionally divided. What matters is whether the theaters form part of a broader strategic contest whose political termination is connected.
Ukraine and Iran remain far from that condition. The publicly reported diplomatic tracks around the two wars remain separate, and no publicly reported settlement framework has made an end to one conflict conditional on an end to the other. The wars increasingly share inputs, providers, and strategic pressure, but their possible endings remain politically distinct. The difference is between sharing inputs and sharing an ending.
How that could change
The history of the 1930s is useful precisely because this kind of configuration does not have to remain stable. Conflicts can begin as separate demands on overstretched powers and gradually become more politically connected as the states conducting them develop reciprocal commitments and increasingly recognize one another’s objectives. British planning illustrates the pressure on the other side of that process. By the late 1930s, planners were explicitly confronting the difficulty of meeting simultaneous threats from Germany, Italy, and Japan with limited resources, which forced choices about where scarce military capacity should be concentrated.
At the same time, the political relationship among the revisionist powers was changing. Germany, Italy, and Japan increasingly recognized one another’s projects and tied their diplomatic positions together. The Anti-Comintern Pact of 1936, the Pact of Steel in 1939, and the Tripartite Pact in 1940 marked stages in that movement towards reciprocal commitment. Their military coordination remained much weaker than that achieved by the Allies, including after the Second World War had begun, but their relationship had nonetheless moved beyond a collection of entirely separate revisionist projects.
A comparable change today would require considerably more than additional weapons transfers. More Iranian-designed systems in Russian service, greater reported Russian intelligence assistance to Tehran, or deeper Chinese political and economic support for Iran would increase strategic coupling. They would tell us less about whether the political purposes of the wars had begun to converge. The stronger evidence would appear if Moscow began conditioning negotiations over Ukraine on American policy towards Iran, if Tehran tied its own settlement to developments in Ukraine, or if reciprocal defense commitments began to connect the theaters more explicitly. Joint political planning or a peace framework encompassing both conflicts would point in the same direction. The clearest indication would come if ending one war became dependent on ending the other.
So far, the relationships have developed differently. Russia has been linked to intelligence assistance for Iran without becoming a belligerent in the Gulf War. Iranian technology helped shape Russia’s drone warfare, while Russia now produces Iranian-derived systems domestically and continues to modify them. China has supported Tehran politically and economically without entering either war as a belligerent. North Korea contributes directly to Russia’s war effort while remaining outside the conflict with Iran. All of this increases the density of the connections surrounding the wars. It does not, on the available evidence, give them a shared political purpose.
The politics of allocation
For the moment, the more consequential shift may be occurring inside the system that provides security to many of the states affected by these conflicts. American security provision is becoming more explicitly hierarchical. The 2026 defense strategy asks Europe to carry primary responsibility for conventional defense on its own continent, regional partners to assume more responsibility in the Middle East, and South Korea to take the leading role in deterring North Korea. American capabilities remain central, but access to them increasingly depends on how Washington ranks competing demands.
The 2025 National Security Strategy adds another layer by giving the Western Hemisphere particular strategic importance and setting out a Trump Corollary to the Monroe Doctrine. It states that the United States will deny non-hemispheric competitors the ability to position threatening military capabilities or own or control strategically vital assets in the hemisphere. Taken together with the 2026 defense strategy, this points towards a security posture in which commitments survive but are increasingly differentiated by region, capability, and urgency.
For allies, that changes the meaning of an American commitment. It is no longer enough to ask whether Washington has promised support. Governments also have to consider what other demands are pressing on the same stocks, forces, and political attention at the same moment. A commitment can remain formally intact while its practical value changes because another theater has acquired greater urgency or priority for particular capabilities.
Some of the behavior already visible makes more sense in this context. Ukraine has turned its accumulated experience against Iranian-designed drones into assistance for Middle Eastern partners. European governments are being pushed towards a larger role in sustaining Kyiv. Taiwan is studying an Iran war in which it has no direct involvement because the conflict reveals how American munitions are consumed, how air defenses respond under pressure, and how quickly industrial capacity can replace what has been used. These states are responding to American power, but they are also responding to the way that power is being allocated.
The wars in Ukraine and Iran are consequently becoming more tightly coupled. Decisions taken in one theater affect the options available in another. Additional capacity supplied to one actor can release resources elsewhere, while heavy consumption in one conflict can narrow the choices facing partners in another. States outside both wars can also be affected as military assets move and strategic opportunities appear. None of this requires the wars to have reached the same political destination.
What we are seeing may therefore be less a single war spreading across theaters than a strategic system in which separate conflicts increasingly transmit pressure through common bottlenecks. That system can become more integrated over time, and history gives good reasons to watch for such a transition. For now, however, the distinction between strategic coupling and political integration remains useful because it tells us what evidence to look for. If political objectives begin to converge, reciprocal commitments become harder to separate, and the terms of settlement start to depend on one another, the diagnosis should change. Until that happens, shared scarcity offers another way of understanding why separate wars can increasingly affect one another without ceasing to be separate.
An integrated war can ration scarce means according to a common political end. Under shared scarcity, the rationing occurs among claims whose ends remain their own.
