When world leaders pull an all-nighter, something has to come out of it. What came out of the 17-hour, Ironman-level endurance test last week in Minsk was a cease-fire deal for eastern Ukraine that mitigates the Kiev government's defeat in a war it could not have won, gave Russian-backed rebels two days to make final territorial gains and freezes the conflict until next year.

The challenge now is to make this cease-fire stick where previous ones didn't. It's not clear if Russian President Vladimir Putin, who has proven to be an unreliable negotiating partner in recent months, will stand by the few concessions he made.

If he can be held to them, it will be a major diplomatic victory for German Chancellor Angela Merkel. My bet, however, is that this is not the final round of high-level talks: The deal resulting from the negotiating marathon is too contradictory to work long term.