NATO expansion has always had convincing pros and cons. This week the pros won. The Western alliance is taking a decisive step eastward, toward an embrace of three new members: Poland, the Czech Republic, and Hungary.
The voices of opposition will, if anything, now grow louder. In the United States, there's still an approval process in Congress. Much more will be heard about the cost of bringing new members' forces up to NATO standards. Billions of dollars could be needed, and Washington will want the burden spread widely.
Russia's complaints, though muted by an agreement that ensures its voice will be heard in NATO councils, still echo. Why antagonize a Russia that's trying to democratize and no longer threatens its neighbors?
On the positive side, NATO expansion could solidify political and economic gains in Eastern Europe. Possible membership in the alliance is a spur to continued reform. A broadening NATO umbrella portends long-term stability and a regionwide climate more conducive to investment and growth.
Russia's nationalists may scream about the encroaching West. But NATO has stretched itself to reassure Russia that it's not being backed into a corner. Hence Russia's newly built-in "say" on alliance policy.
That "say" hasn't been put to the test. But the test could come if the initial three new NATO entrants grow into the next three or four, as France and other current members hope - reaching ever deeper into what Russia still considers its natural sphere of influence.
Such "spheres" may be the heart of the problem. NATO expansion implies a different mission from the old bulwark against communist aggression.
Tomorrow's NATO could be an insurance policy against a breakdown of order within Europe's wider neighborhood - benefiting everyone, nonmembers, members, those with a "special relationship" (Russia), and neutrals alike.
This more inclusive, less confrontational NATO is even now having a trial by fire in Bosnia. And the Eastern Europeans are already playing important roles in the multinational forces in the Balkans.
NATO couldn't retain its cold-war identity. Change was inevitable, and not according to a clearly articulated step-by-step plan. Rather, it's coming ad hoc, on the heels of events. The end result could turn out well - if the partnership with Russia is carefully nurtured, and if new members realize the responsibilities are at least as great as the benefits.