Last year the U.S. Senate overwhelmingly approved the expansion of the Atlantic alliance. Whereas some advocates of enlarging NATO, particularly Eastern European leaders for whom the Soviets' iron grip is an all too recent memory, stress the extension of the alliance's traditional deterrent function, others acknowledge that Russia is in no position to reconquer its former empire. Rather, they argue that membership in NATO would stabilize the region by filling the power vacuum and eliminating the need for security competition. Traditionally a volatile area, East-Central Europe is rife with potential irredentist and ethnic conflicts, and NATO can help arbitrate and limit these disputes. Critics have denounced the move as unnecessarily provocative to Russia, and they have also decried its hefty cost. But they have not challenged the claim that alliances create zones of peace.