Huh?
When Hitler invaded, the Russians didn’t say, “well, let’s not invade Germany. We don’t want to escalate.” They invaded Ukraine, so Ukraine would be well within its rights to launch some serious attacks inside Russia. But right now, it’s all they can do to foil the further advance of Russia into Ukraine, and also f@#$ with Crimea, and retake a little territory here and there in the east, so it’s a moot point.