Adolph Hitlers armies tactically retreated all the way back to the Tiergarten in Berlin in 1945 and he was still winning until he was dragged out of his bunker a bit dead.swimming too
Napoleon retreated all the way back to Paris with the straggling shredded remains of his Grande Armee after he failed to invade Russia.
The U.S. armies tactical retreat from Vietnam is another notable success in losing a war against a better motivated and smaller enemy.
Putin can learn from this and lose better.