For nations that have them, nuclear weapons are thought to provide almost blanket protection against aggression by external forces. As the theory goes, deployment of atomic bombs brings such total destruction that no one in their right mind would dare attack a country that has a vast nuclear arsenal. This thinking drives the cautiousness of the West in its support for Ukraine in the war against Russia.

Given how established this “porcupine” theory is, many people have been surprised by the Kremlin’s muted reaction to Ukraine’s recent incursion into Russia’s Kursk region. Ukrainian forces are said to occupy about 500 square miles of Russian territory currently. Putin has, thus far, only referred to the border penetration and land occupation as a provocation, and Russian forces have been unable to push the Ukrainians out.

In the period since the collapse of the Soviet Union, there have been several iterations of Russia’s nuclear doctrine. A 1997 version allows the deployment of nuclear weapons “in case of a threat to the existence of the Russian Federation as an independent sovereign state.” Some observers have noted that because the land mass occupied by Ukrainian forces in Kursk is relatively small and strategically unimportant, the incursion does not pose an existential threat to Russia. That, in their view, perhaps explains why the Kremlin is acting as if Ukraine didn’t cross a red line by its invasion.

That assessment is quite plausible. However, the lack of Russian reaction could also be because even these current occupants of the Kremlin know a ridiculous argument when they see one. Perhaps they are having trouble invoking their nuclear doctrine because it is the threat they posed to another sovereign nation’s existence that triggered the incursion to begin with.

Putin launched his full-scale invasion of Ukraine in early 2022 after claiming that Ukraine’s attempt to join NATO posed an existential threat to Russia. There are two problems with his argument. First, Russia has the largest stockpile of nuclear weapons in the world. That is a gigantic waste of space if Putin fears that all that arsenal is not much of a deterrent against external attack.

Second, as stated in his country’s nuclear doctrine, Russia will do whatever is necessary, including use of nuclear weapons, to protect its sovereignty. Ukraine’s desire to join NATO has always been about protecting its own independence. It is the very choice that many of the former Soviet-bloc countries made to preserve their hard-won sovereignty when the Soviet Union collapsed. Why does Putin think another sovereign nation, Ukraine, should subordinate its interests to those of Russia so the emperor in the Kremlin can sleep peacefully at night? What if Ukraine were to complain that being a next-door neighbor, all those deadly weapons amassed on Russian soil posed a threat to it and hence call for their destruction or removal and placement elsewhere? Would Putin acquiesce?

Quite absurdly, across the world, there seems to be widespread acceptance of the notion that the interests of large, powerful nations supersede those of smaller, weaker ones. Should sovereignty mean one thing for the big boys and something else altogether for the little guys? Ukraine’s incursion into Kursk and occupation of territory there should be seen as nothing more than self-defense. There couldn’t have been any red lines along the route that Ukrainian soldiers took to get there.