As the EU takes steps toward federalization, NATO should expand into the eastern parts of Europe. Because of disagreements about policy, it will be a long time before the EU will be able to form a central military. NATO can fill that hole in the interim by bringing EU nations together under a common plan about how to handle aggression against any one nation that is a member.
Expanding NATO further eastward will jeopardize the effectiveness of the alliance by adding countries with less developed and sophisticated military capabilities. In addition, further expansion would be an unnecessary provocation of Russia and increase the likelihood of conflict with it and other countries close to Russia. There are few, if any, benefits from expansion that would justify taking such risks.