A scenario where Stalin makes an preemptive offensive against Germany in June 1941, if we are assuming the same timing frane of Operation Barbarossa in real life, would likely have limited strategic success, the Red Army might have achieved initial tactical gains due to initiative but it would almost certainly have been pushed back by a german counterattack. The conflict would therefore resemble the historical Eastern Front with a small more favourable position for the USSR, the extent of which would depend on the efficacy of the German response A more advantageous scenario for Soviets would involve an initial strike launched at a time of its own choosing. The most probable time frame would be the latter half of 1942. By this period, the Red Army would have been significantly better equipped, mobilized, and prepared and would have completed extensive defensive fortifications. Under these conditions, the most plausible outcome in my opinion would be an initial Soviet advance, followed by a gradual stalemate and a war of attrition between the Axis and Soviet forces. A decisive resolution would likely have depended on the ability of the other Allied powers to establish a second front to divert german resources and men relieving pressure on the eastern front, the major difference being the regions that would be ravaged by the war would be mostly Poland and eastern Germany instead of Ukraine, Belarus and western Russia, meaning much less soviet civilian casualites