The United States drew closer to its G7 allies on Friday, overcoming differences, at least momentarily, to back Ukraine's territorial integrity and warn Russia to follow Kyiv in accepting a ceasefire or face possible further sanctions.

Russia struck a sedate tone on Friday but acknowledged grounds for cautious optimism, after only backing the "idea" of a U.S. brokered 30-day ceasefire with firm caveats.

The last time Ukraine signed a peace accord with Russia, 10 years ago, it brought only sporadic violence, mounting distrust, and eventually full-scale war. Here’s what we can learn from that history.