This piece was originally published on Just Security, an online forum for analysis of U.S. national security law and policy. Putin is losing the war he started against Ukraine. Russia still holds Ukrainian territory, but Ukraine’s forces are advancing. With Russia mostly on the defensive, its forces are behaving brutally but also erratically: not only are they targeting Ukrainian civilian infrastructure, they’re also threatening nuclear escalation and then backing away, and pulling out of — and then coming back into — the Black Sea grain-export deal. Ukraine’s victory is no sure thing. The battle lines could stabilize for the winter….