NATO has recently expanded to include several eastern European, formerly communist states. This article uses empirical evidence on alliances and war to argue that this expansion and plans to expand NATO even more may pose a serious threat to international peace since the expanded alliance possesses two of the three major factors that have been found to be associated with war-prone alliances. In addition, it is argued that the expanded alliance may greatly hamper Russia's transition to democracy. The article concludes that a better long-term policy for NATO states to pursue would be an expansion that included Russia but that would be restructured to resolve outstanding territorial disputes in ways similar to the Congress of Vienna of 1815. The potential impact of this expanded NATO on political transitions in the Balkan states is also discussed.