In this chapter, I analyze whether it was instrumentally rational for the CEECs to seek membership in NATO and for the NATO members to admit CEECs as full members to their alliance. If all states involved in the decision could expect to reap higher net benefits from the limited first round of enlargement than from other NATO–CEEC relationships, the rationalist explanation would be successful. I will argue, however, that rationalist institutionalism only succeeds in explaining the CEECs' bid to join NATO. It cannot account for NATO's enlargement decisions.

The CEECs and NATO membership

The security approach to enlargement, especially balance-of-threat theory, provides a largely convincing explanation of why the CEECs wanted to join NATO.

Russia was a potential threat to the CEECs. Although the Soviet Union ceased to exist, the Russian Federation has remained by far the most powerful country among the CEECs. It inherited most of the territory, population, and military forces of the Soviet Union and it is the only nuclear-weapon state and “great power” among the post-communist countries. Russia is not only more powerful than each individual CEEC but also poses a potential threat to them. An Eastern European state itself, Russia is located in the geographical proximity of the CEECs, and although Russia's offensive capabilities are not as high as those of the former Soviet Union, they remain considerable.