Since the “Epic Fury” operation has been striking Iran since February 28, 2026, the increase in armed conflicts marks the end of a certain idea of deterrence. From Ukraine to Gaza, from the Caucasus to the Middle East, something has been disrupted in the security architecture that had prevented the return of conquest wars since 1945. Not a third world war identical to the first two, but something potentially more insidious: a series of conflicts that no one seems able to contain.
Since 1945 and the first use of nuclear explosives, a belief has structured Western strategic thinking: the existence of these “absolute weapons” makes any war of conquest between major powers unthinkable, making the territory of nuclear-armed states inviolable. These countries could only confront each other indirectly, in limited wars, whose intensity would never reach the hyperbolic violence of the first two global conflicts.
However, this certainty has been shattered. By invading Ukraine, a country whose independence and security it had guaranteed within the framework of the Budapest Memorandum in 1994, Russia used its atomic arsenal as a shield (without risking direct involvement of the United States) to conduct a conventional war of conquest. This Russian invasion has caused a profound disruption of deterrence mechanisms, the consequences of which may not have been fully diagnosed.
A Shift in the Threshold
The extent of what is possible under the “nuclear umbrella” without triggering its collapse has significantly increased. The war in Ukraine showed that a high-intensity conventional confrontation, pursuing explicit territorial annexation objectives, could unfold without the nuclear threat being activated, neither by the aggressor to protect its gains nor by the states supporting the defense of Ukraine to end it.
The concept of a nuclear “threshold,” theorized in 1960, assumed a precise line beyond which atomic war became certain. Since the war in Ukraine, this notion can no longer be strictly understood. In reality, behaviors obey more complex mechanisms: there is an area of uncertainty, an intermediate space where an infinite number of hostile acts remain possible without automatically leading to ultimate escalation.
In other words, we observe an elevation of the threshold at which the behavior of certain actors becomes intolerable. And it is precisely this elevation that opens a window of opportunity for “revisionist” powers, meaning those wishing to change the rules of the system to their advantage.
For example, by using force to annex new provinces and disregarding a cardinal principle of the United Nations: the inviolability of borders. According to this principle, borders cannot be modified by force, and any change in their delineation can only be made according to existing internal administrative limits. This principle had only experienced rare exceptions in seventy years (Tibet acquired by China in 1950, Kashmir, the border between the two Koreas, Israeli-Arab wars, Cyprus-North).
The Return of Wars of Conquest
Here we see the most serious risk emerging: not a Third World War deliberately declared by a single power or group of powers, resulting in total atomic warfare, but a multiplication of simultaneous conventional conflicts exhausting American capacities and will of response, which could be called a “world war under the threshold” (i.e., not initially provoking nuclear weapon use).
In the past five years, the most significant ruptures have come from the nuclear powers themselves. Russia tried to subjugate Ukraine through a lightning offensive and formally annex five provinces, before settling into a war of attrition with lasting consequences for the European order. Israel, an undeclared nuclear power, responded to Hamas’ attack on October 7, 2023, with unprecedented military operations in Gaza, Lebanon, Syria, against the Houthis in Yemen, and finally against Iran, following its doctrine of “disproportionate response.” The United States, far from being spectators of the system’s deregulation, have become one of its agents: the operation in Iran was launched without UN authorization or consultation with Congress, and Washington openly threatens some NATO members, undermining the institutions it had contributed to build. The guarantor of the previous order, tired of financing the alliance, has thus launched a brutal reform that disrupts its architecture and threatens to make it falter.
Other conflicts, without involving nuclear arsenals, have been launched with correlation to these confrontations. In September 2020, Azerbaijan launched its first victorious offensive on Armenia, gradually leading to the disappearance of the Republic of Artsakh and the exile of more than 100,000 Armenians, without the international community being able to prevent this exodus. These conflicts are further evidence that the return of restricted local wars was not an accident but a significant trend, adding to the insurgency struggles of previous decades.
Certainly, not all these wars have resulted in significant border changes, but neither the United States nor its strategic competitors are able to regulate all of them simultaneously. The United States could once balance regions and tensions through offshore balancing, but the rise in emergencies and conflicts makes it increasingly difficult for them to act with the same effectiveness. The proliferation of conflicts shows that this has become much more challenging. This allows much greater leeway to local actors to alter their relationships with neighbors.
The article is complemented by an URL and bio of the author, Antony Dabila, on international relations at Sciences Po.
