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Pentagon plan to move weapons in Eastern Europe is measured response.

A Pentagon proposal to position heavy weaponry, but not troops, in front-line NATO nations would represent a significant but measured response to Russian provocation. The predictable Russian pushback and subsequent "nuclear saber-rattling" — in the words of NATO Secretary General Jens Stoltenberg — explains why the West needs to send a strong signal to Russia, as well as to more vulnerable Baltic and Eastern European states.

Several of these states have made it clear that they would prefer permanent troop deployment as well, but the movement of materiel that could be quickly used by as many as 5,000 U.S. troops is sufficient for now. The equipment, according to the New York Times, might include battle tanks, infantry fighting vehicles and armed howitzers, and may be distributed between three Baltic countries — Lithuania, Latvia and Estonia — as well as Poland, Romania, Bulgaria and maybe even Hungary.

Many in these former Soviet satellites are understandably wary, not just because of Russia's annexation of Crimea and backing of pro-Russian separatists in Eastern Ukraine, but because of provocative maneuvers that risk turning a Russian military miscalculation into a true crisis.

Although the backdrop is Ukraine, the Pentagon plan might have little effect on mitigating that crisis. Rather, it represents reassurance to allies and a warning from NATO to an increasingly adversarial Russia.

The plan "has to be considered very carefully in the context of sanctions and diplomatic isolation — these kind of moves can be potentially dangerous at the same time they are reassuring," said Mary Curtin, diplomat-in-residence at the University of Minnesota's Humphrey School of Public Affairs. "There is consensus that the effort needs to continue to stop Russia, and this prepositioning of military equipment has more of an effect of calming the Baltic states and making them more sure than it does have a direct impact on what's happening with Ukraine."

The efforts to stop Russia should ultimately depend on diplomacy, not on military means, so it's critical that the European Union proceed with plans to extend economic sanctions for at least another six months.

Sanctions and lower oil prices will send Russia into recession, but Putin has pledged to raise military spending nonetheless. The West must be prepared for that, while continuing to seek diplomatic outcomes in Ukraine. It also must bear in mind that Russian cooperation will be needed for an accord with Iran over that country's potential nuclear weapons program and possibly even for some kind of settlement to end the global destabilization caused by Syria's disintegration.

Putin may have calculated that he could erode the NATO alliance. Instead, he seems to have strengthened it. Now is the time for Western leaders to use this unity wisely.