The dangerous and irresponsible sea-skimming flyovers by Su-24 attack aircraft of the U.S. Navy destroyer USS Donald Cook operating in international waters in the Baltic Sea a few days ago, followed by a Russian aircraft’s hazardous flyby of a U.S. reconnaissance aircraft in international airspace just a few days later, are a reminder that, while many hope for a relaxation of tensions with Moscow, that is likely to be wishful thinking. Whether we want it or not, relations between the United States and its NATO allies on the one side and Russia on the other are likely to remain distrustful and tense. More to the point, they are likely to remain shadowed by the possibility of crisis and even conflict. Moscow’s willingness to conduct brazen violations of international rules, its revanchist attitude towards elements of its former empire, its resurgent military power, and its sense of deepened alienation from the West all point towards the persisting potential for a standoff with the Atlantic alliance.

This means that the United States and its NATO allies need to be prepared for such an eventuality — and, better yet, prepared to such a degree that Moscow will recognize that pushing on the alliance will be too costly and risky to be worth trying. The U.S. defense budget request for next year (and accompanying commitments to further deployments in Europe), which is currently being used by the relevant House and Senate committees to inform their markups of the Fiscal Year 2017 defense authorization and appropriations bills, represents a major step forward in achieving this goal. It appropriately concentrates on the threat to U.S. and allied security posed by “great power” potential adversaries. It plusses up investments in key next-generation technologies in areas like space, unmanned systems, and cyber, while also preserving funding for the modernization of the nation’s nuclear deterrent. And it allocates $3.4 billion for the European Reassurance Initiative, while committing to reestablishing the permanent presence of an armored brigade combat team in Europe to strengthen the American posture there in the face of the most serious near-term threat to U.S. and allied interests — a resurgent and revisionist Russia. This represents a series of significant and commendable improvements.

But they are not enough. And this is not because more is always better. Rather, it is because even this augmented posture is considerably below what the alliance needs for an effective conventional deterrent. This is especially urgent because analysis by the RAND Corporation and other sober sources suggest that, if the Russians opted to do so, they could quickly mobilize with minimal warning and then rapidly bypass or overrun the presently envisioned U.S. and allied forward “tripwire” defense forces, en route to overrunning the Baltics in as little as two to three days. Simultaneously, Russian artillery, airpower, submarines, and long-range missiles could maul NATO forces as they attempted to surge from rearward locations in defense of their embattled allies.

So what should the alliance do beyond what the Obama administration is proposing? In order to most effectively deter Russian adventurism, NATO should want the most formidable deterrent, one that persuades the increasingly capable Russians in the most concrete ways that embarking on even limited military aggression would simply be too risky and costly. This means fielding a conventional military posture that includes substantial, potent forces permanently deployed forward in Central and Eastern Europe that can assuredly arrest any Russian military thrust into NATO member-state territory. Such a posture should be able to hold off, or at least bog down and bloody, a Russian force — even if it cannot quickly defeat it — until NATO can surge the forces needed to prevail forward. This is not a revolutionary military idea, but rather what a classic conventional deterrent should look like.

Yet the administration’s proposed deterrent does not look much like this. For instance, the single U.S. armored brigade planned for deployment will likely be divided into contingents that will be rotated through numerous Central and Eastern European countries. Nor are our European allies, who must also carry their share of the burden in a more constrained budgetary environment and in the face of a more challenging Russian military, proposing anything more substantial. The dispersed, transient force that would result from this risks being inappropriately configured and positioned, as well as insufficiently manned or armed, to impose serious costs on a Russian assault. Indeed, RAND wargaming, for instance, indicates that the alliance would need six to seven combat-ready brigades — plus supporting air and naval forces — in Europe just to avoid losing in the face of a Russian thrust. The modest force proposed therefore risks being circumvented, if not simply avoided. Indeed, given the length of the Baltic states’ borders with Russia, such a posture could offer the Russians the ability to force NATO to act tactically aggressively first — or even save Russia from having to fire a shot in anger at all — thereby missing the fundamental value of a forward deterrent.

Accordingly, the United States and its NATO allies should focus on developing the capabilities to enable their forces to confront a growingly sophisticated Russian military, and particularly forces sized and equipped to fill the dangerous gap in the alliance’s forward defense in the east. In line with this, the United States and key allies should concentrate on initiatives like obtaining rapidly procurable air defense, electronic warfare, and artillery systems that will enable ground forces to hold the line against a modern Russian onslaught. These would prepare the alliance to defend against and weather Russian missile strikes; enhance force-wide communications systems’ security, resiliency, and joint/allied interoperability; and improve capabilities for air and sea operations — including the flow of U.S. Army and Marine reinforcements to Europe — in the face of Russia’s potent anti-access/area denial umbrella. In the United States, Congress should fund the resources necessary to realize these measures.

But this effort also cannot only be about the United States. Elsewhere in NATO, member states should not only strive to meet their 2-percent defense spending commitment, but, particularly given the political obstacles to meeting this criterion, direct existing military forces much more efficiently toward deterrence of Moscow. NATO’s larger European members, such as Germany, should contribute their own troops, particularly heavy forces, to the defense of their treaty allies to the east, including by stationing them as part of multinational permanent forward units. This would signal that the entire alliance comprehends the danger — and is resolved to address it. Little else would be so likely to communicate to Moscow that any thrust, however potent, would elicit a resolute and ultimately availing response from the Atlantic alliance.

Elbridge Colby is the Robert M. Gates Senior Fellow at the Center for a New American Security. Jonathan Solomon is a senior systems and technology analyst at Systems Planning and Analysis, Inc. This piece is adapted from the authors’ article “Facing Russia: Conventional Defence and Deterrence in Europe” in the December 2015 – January 2016 issue of Survival. The opinions expressed herein are solely the authors’ personal views.

Photo credit: Spc. Cassandra Simonton, U.S. Army Europe