This is a very lame excuse to start killing people. What counts is a written treaty or it is nothing. The Budapest Memorandum was proper treaty signed in public that committed everyone. If Russia needed its "assumptions" met then it should have insisted they be included in the treaty or another treaty. The problem is the people of Eastern Europe had experienced Russian Imperialism and they wanted no part of it and so sought the protection of NATO so they would never agree. Russia has no one to blame for its problems but itself.