CNN  —  The ceasefire proposal put forward by the United States on Tuesday and accepted by Ukraine is part of a plan, said US Secretary of State Marco Rubio, “to end this conflict in a way that’s enduring and sustainable.” It’s a promise fraught with risk for Ukraine. The last time it signed a peace accord with Russia, 10 years ago this February, it brought only sporadic violence, mounting distrust, and eventually full-scale war. “I told President Trump about this,” Ukraine’s President