The North Atlantic Treaty Organization was reborn last week. The alliance has added seven new members, all former Eastern bloc countries, extending NATO's territory to Russia's borders in the Baltic and to the Black Sea. Yet unlike the last round, this time Moscow accepted the expansion without protest. While winning Russian acquiescence is a victory in itself, NATO faces new challenges. Not only must it prove that it will not be immobilized by its size; it must be even more nimble to respond to the new security challenges that its members now face.

It is significant that NATO held its historic meeting -- ratifying the "big bang" -- in Prague. Czech President Vaclav Havel has long campaigned for the inclusion of Eastern European governments in NATO and the European Union to solidify democratic transition in those countries. The expansion of those organizations to include former adversaries -- Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia and Slovenia -- is a fitting gesture as Mr. Havel prepares to leave office. Since 1999, NATO has added 10 European nations. (In fact, the new countries have only been extended membership; they do not actually become members until May 2004 after their legislatures and those of the 19 current members ratify expansion.)

Although most of the attention was focused on the members -- old and new -- attending last week's meeting, the most important nations may have been those not present: Russia and Iraq. The relative ease with which the seven new members joined NATO testifies to the new relationship Moscow has developed with its former adversary. This was institutionalized in the accord signed by Moscow and NATO last May. It established a special relationship between the treaty organization and Russia, which, while not giving Moscow a veto over NATO decisions, did give it additional weight and made it clear that NATO was sensitive to its concerns.