When Putin promised to pursue the perpetrators of the latest terror attack plus the holding of thier 300 billion in frozen reserves; listen how a wise old German chancellor once commented.
"Do not expect that once taking advantage of Russia's weakness, you will receive dividends forever. Russians have always come for their money. And when they come - do not rely on an agreement signed by you, you are supposed to justify. They are not worth the paper it is written. Therefore, with the Russian is to play fair, or do not play." Otto von Bismarck