神圣同盟
Since the war against Napoleon, Russia had become deeply involved in the affairs of Europe, as part of the "Holy Alliance." The Holy Alliance was formed to serve as the "policeman of Europe." However, to maintain the alliance required large armies. Prussia, Austria, Britain and France (the other members of the alliance) lacked large armies and needed Russia to supply the required numbers, which fit the philosophy of Nicholas I. When the Revolutions of 1848 swept Europe, however, Russia was quiet. The Tsar sent his army into Hungary in 1849 at the request of the Austrian Empire and broke the revolt there, while preventing its spread to Russian Poland. The Tsar cracked down on any signs of internal unrest.