Ukraine Not Joining NATO So Why Does Putin Worry?

Putin opposes NATO's missile defense presence in Romania and a similar base under development in Poland, saying they could be converted to offensive weapons capable of threatening Russia. (AP)

At the core of the Ukraine crisis is a puzzle: Why would Russian President Vladimir Putin push Europe to the brink of war to demand the West not do something that it has no plan to do anyway?

Russia says NATO, the American-led alliance that has on its hands the biggest European crisis in decades, must never offer membership to Ukraine, which gained independence as the Soviet Union broke apart about 30 years ago. Ukraine has long aspired to join NATO, but the alliance is not about to offer an invitation, due in part to Ukraine's official corruption, shortcomings in its defense establishment, and its lack of control over its international borders.