Limited war is back.

• Author: Grygiel, Jakub

Europe needs to rearm and defend itself to cope with a new military threat. The American security umbrella--in both its conventional and nuclear forms--is no longer adequate, particularly on NATO's vulnerable eastern flanks. Indeed, the extended deterrent provided by the United States to its most exposed allies may not be well suited to inhibiting attacks similar to Russia's recent incursion into Ukraine, which displayed all the hallmarks of the newly popular limited conventional wars--brief and decisive, violent and yet very restrained. The purpose of such conflicts is to achieve a quick fait accompli in a geographically circumscribed area through limited force-- in this case, paramilitary means followed by Russian regular forces. It is difficult to deter such a threat through the promise of retaliation, which by its very nature must occur after the facts on the ground have already been changed. A threat of retaliation is simply less credible when the enemy has achieved his objective through a low-intensity action. What are needed instead are strong local military capabilities--a preclusive defense--that increase the costs of that limited attack. Europe must start to defend its border rather than indulge in the belief that the traditional formula for deterrence, based on retaliation and the extended deterrent provided by the United States, will suffice. It won't.

Whereas limited warfare went out of fashion in the West after Vietnam, Russia regards it as a central part of its military doctrine. It has practiced it in Georgia, Crimea and eastern Ukraine, and presumably rehearses it elsewhere. It is therefore imperative to study anew the challenges presented by such a form of sanguinary behavior. "Limited wars" have several distinctive features. First, they are characterized by self-imposed restraint in the political objective sought and the level of force used. The aggressor could escalate the confrontation, but chooses not to. The purpose of limiting the use of force is to avoid some reaction that would undermine the political objective sought in the conventional assault. In the case of today's Russia, the purpose is to extend influence and control westward without eliciting a strong response from NATO and the United States. Moscow recognizes the clear military superiority of its main rivals and consequently desires to avoid a pitched confrontation that it would lose. Hence, its use of force is calibrated to be sufficient to conquer pieces of Ukraine but not so large and violent that it would prompt a unified political, economic and military reaction from the West.

Russia is as clear regarding what it wants to avoid as it is concerning what it wants to achieve. Moscow's objectives are limited: a small and quick territorial grab rather than a massive invasion (at least for now). There is no drive to the capital (Kiev, in this instance) or attempt at full conquest but instead a speedy push inside the neighboring state followed by a sudden, self-imposed stop. It is a "jab and pause" style of war fighting meant to achieve a swift and limited fait accompli. A rapid conquest of Crimea or parts of eastern Ukraine is followed by a pause and apparent openness to seek a mutually acceptable negotiated settlement. But the limited objective has already been achieved, and the quick suspension of violence is a sign of the satisfaction of the original goal.

A limited war is also characterized by limited means. The aggressor state carefully tailors its methods to the goal it wants to achieve--and the reaction it wants to avoid. Minimal violence is employed. The potential for escalation is made clear but held in reserve. In the case of the Crimean invasion, the Russian operation started anonymously with unmarked troops (dubbed "little green men" by Ukrainians), an indication that Moscow was uncertain about how local Ukrainian forces would react. In the event of determined opposition, Russia maintained the option of either escalating with larger forces or, should Western powers come to Ukraine's aid militarily, halting the operations of the unmarked troops.

The aggressor, in fact, constantly has to weigh the value of the limited objective against the risk of the rivals' response. The higher the value of the objective, the more risk it is willing to accept. In Ukraine, it is plausible that Moscow's desire to avoid a military clash with NATO members (including in the form of Western-armed and -trained Ukrainian forces) is greater than its desire to occupy Crimea. Russian military might is impressive when compared to that of its neighbors, but Moscow cannot sustain a prolonged conflict with Western-supported forces and certainly cannot do so against NATO member states. But the risk of a Western military response was and remains negligible, and Russia achieved its objective in Crimea with ease.

Two main challenges present themselves when crafting a response to a limited war waged by a rival. First, it is politically difficult to answer a restrained military attack. As the Crimea case illustrates, Western policy makers face significant hurdles when attempting to mobilize public opinion in...