http://online.wsj.com/news/articles/SB10001424052702303802104579449571957045910#printMode

Vladimir Putin and his American apologists like to blame NATO’s post-Cold War expansion for his territorial conquests, which ignores that the alliance refused in 2008 to let Georgia and Ukraine even begin the process of joining. Those are the two countries the Russian has since carved up, and the question now is whether Russia’s expansionism will slap Western leaders out of their self-defense slumbers.

NATO Secretary-General Anders Fogh Rasmussen sounded the alarm last week in a visit to Washington. “I see Crimea as an element in a greater pattern” of Russian strategy, he told an audience at the Brookings Institution. Moscow’s annexation of Crimea, he said, is “a wake-up call” that “must be followed by increased European investment in defense.” He might have included the U.S.

The combined GDP of NATO’s 28 member states tops $30 trillion. Yet with few exceptions, most notably Poland, NATO defense expenditures have declined since the end of the Cold War. The nearby table shows the relative defense spending in 2013 for some key NATO countries as a share of GDP. Only four members—the U.S., U.K., Greece and Estonia—spent at least 2% of GDP on defense.

At 1.9%, France last year fell short of the 2% that is supposed to be the technical requirement for membership. Mr. Rasmussen’s Denmark spent 1.4% of its GDP on defense, Angela Merkel‘s Germany 1.3%, Italy 1.2%, and Spain 0.9%. This is what a country spends if it thinks its main security threat is Belgium.

And the trend is down, as a majority of NATO members reduced defense spending in 2013. Among the more drastic defense cutters last year were Canada (7.6%), Slovenia (8.7%), Italy (10.3%), Hungary (11.9%) and Spain (11.9%).

The U.S. reduced its overall spending by an estimated 2%. That might not sound like much, but American spending comprised 72% of all NATO defense expenditures in 2013. Under President Obama’s latest budget proposal, U.S. defense spending will fall from 4.6% of GDP in 2011 to 3.5% in fiscal 2015 and 2.9% by 2017 when he is supposed to leave his successor a country stronger than he inherited. On present trend it will be weaker.

The Obama theory of “collective security” is that as the U.S. retreats from its historic commitments in Europe and the Middle East, allies will step up to deter aggressors and protect Western interests. NATO budget cuts suggest otherwise.

The cuts have created “gaps in meeting core NATO tasks” and resulted in “forces that are not ready, not trained, and not sufficiently equipped,” according to a 2012 study by the U.S. National Defense University. In plain English, this means that if Vladimir Putin sets his sights on NATO’s eastern periphery—by targeting the Baltic states, for example—the alliance may not have the capability to resist even if it has the political will.

European powers in recent years have shelved entire divisions and weapons systems. The British Royal Navy doesn’t operate a proper aircraft carrier. The Netherlands in 2012 disbanded its heavy-armor division, and France and the U.K. each now field a mere 200 main battle tanks. France has cut its orders of Rafale combat jets to six a year from 11. This isn’t even a Maginot Line.

Most alliance members are also dangerously demobilized: Germany last year announced plans to cut its troops to no more than 180,000 from 545,000 at the end of the Cold War. The French military has shrunk to 213,000 from 548,000 in 1990. The U.K. now has 174,000 armed forces, down from 308,000 in 1990.

NATO countries have also been deferring maintenance of major equipment and cutting back weapons inventories. Such neglect, normally hidden, became apparent in 2011 when Britain and France ran out of precision-guided munitions during NATO’s Libya campaign.

Russia takes military matters seriously. The Putin regime has increased defense spending 79% over the past decade, according to a Brookings study. Defense expenditures amounted to 4.5% of Russian GDP in 2012, the World Bank reports. After a period of post-Cold War neglect, Moscow has been closing its capability gaps, including the upgrade of its Soviet-era fleet of military-transport aircraft and interceptor jets. Russia’s state-run media celebrated these developments a few weeks before Mr. Putin’s Crimean incursion.

Justifying cuts to Germany’s military budget, then-German Defense Minister Thomas de Maiziere predicted in May 2013 that “it is more likely the Bundeswehr will in future be employed in areas of crisis and conflict around the world than in defending the country.” Such thinking warms Mr. Putin’s heart—and may increase his territorial appetite.