Jeffrey Simon, Senior Fellow with the Institute for National Strategic Studies of the National Defense University.

The original post-world war II membership of NATO was 12 nations committed to presenting an effective barrier to Soviet aggression. In time, NATO embraced 16 member states and represented the strongest form of transatlantic bond. Now three candidates - Poland, the Czech Republic, and Hungary have been nominated for membership. Jeffrey Simon explains the criteria for expansion and reviews the prospects of several other countries that might be invited next year.