Since 1945 and the first use of nuclear explosives, a conviction has shaped Western strategic thinking: the existence of these “ultimate weapons” makes any war of conquest between major powers unthinkable, rendering the territory of states armed with nuclear weapons inviolable. These countries could only confront each other indirectly, in limited wars, whose intensity would never reach the hyperbolic violence of the first two world conflicts.
However, this certainty has been shaken. By invading Ukraine, a country whose independence and security it had guaranteed under the Budapest Memorandum in 1994, Russia used its atomic arsenal as a shield (without risking direct involvement of the United States) to wage a conventional war of conquest. This Russian invasion has disrupted deterrence mechanisms profoundly, with consequences that may not have been fully diagnosed.
The concept of a nuclear “threshold,” theorized in 1960, assumed a precise line beyond which nuclear war became certain. Since the start of the war in Ukraine, this notion can no longer be strictly understood. In reality, behaviors adhere to more complex mechanisms: there is an area of uncertainty, an intermediate space where an infinite number of hostile acts are possible without automatically escalating to the ultimate level.
In other words, there is an increase in the threshold at which the behavior of certain actors becomes intolerable. And it is precisely this increase that opens a window of opportunity for “revisionist” powers, wanting to alter the rules of the system in their favor.
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 altered by force and any modification can only be made within existing administrative boundaries. This principle has been applied in decolonization and the end of the USSR, with few exceptions in seventy years.
The return of wars of conquest is now apparent, with conflicts threatening to escalate and possibly merge, leading to a scenario where the global order faces significant challenges. The recurrence of regional conflicts, along with the inability of global powers to regulate and contain these conflicts simultaneously, introduces new complexities and risks to international stability.
As tensions rise and conflicts intensify, the need for new mechanisms to regulate these conflicts and prevent them from escalating becomes crucial in avoiding a potential breakdown of the international system. This requires not only restoring shared norms on the use of force but also constructing a new security regime based on regional power dynamics that can function independently of a single, increasingly erratic global guarantor.
