Europe is in the throes of its most dangerous crisis since the end of the cold war. When President Viktor Yanukovich was toppled in Kiev eight days ago, the world wondered how the Kremlin would respond to the fall of its cherished ally and the threat that Ukraine might shift westwards. In the past three days, Vladimir Putin, president of Russia, has given his uncompromising answer.

President Putin has effectively annexed Crimea, detaching the peninsula from the rest of Ukraine to which it legally belongs. In a propaganda campaign of often unfounded allegations of mistreatment of Russian-speaking communities in eastern Ukraine by Kiev’s new leadership, officials are now attempting to build a case for military intervention in the east.

By entering Ukraine as a punishment for its revolution, Mr Putin has not only shown brazen disregard for international law. He has also created the very real possibility that Ukraine and Russia will be engulfed in a bloody conflict that could last for years.