Vladimir Putin’s Sept. 21 speech — alongside Russian mobilization and sham referenda in Ukraine’s occupied east and south — demonstrates that the Russian leader’s immediate war aims have shifted. As always, Putin seeks to let the context shift, grab what he can, and await a better set of circumstances. Putin’s goal is now a stalled conflict, not a frozen one. The West must deny him this victory by assisting Ukraine in another counteroffensive before winter, while preparing a series of responses to Putin’s threat of nuclear escalation. Two weeks ago, the Ukrainian military, with only a limited force — around…