Last week NATO held its most important summit of the post-Cold War era and one of the most important in its 65-year history. The Russian "incursion" into Ukraine — the refusal to openly acknowledge that it is in fact an "invasion" is an indication of NATO's problem — is a literal "call to arms" and a reminder of the organization's original and enduring purpose: to defend member states against aggression from the East.

NATO has responded with a three-part plan to set up a rapid reaction force, increase training and boost European member states' defense budget. The declaration of resolve must be followed by effective action; empty rhetoric will not only expose NATO as lacking a shared purpose but could genuinely threaten the security of member states.

A few months ago, the Wales summit was expected to focus on defining a common mission for NATO after the decade-long Afghanistan stabilization operations ended. In addition, U.S. and NATO officials would demand serious financial commitments from members who had largely ignored the need to step up defense spending as security challenges multiplied and diversified. In fact, military spending by NATO members has fallen 20 percent during the last five years, and just four — the United States, the United Kingdom, Greece and Estonia — have lived up to the longstanding promise to spend at least 2 percent of gross domestic product on defense.