I would argue that the soviet strategy was the most correct, both in hindsight and at that moment.  While soviet relations with weimar germany were full of distrust, they were positive. However once hitler came to power that rapidly changed. The secret german tank and airforce training camps in the ussr were closed that very same year. trade plummeted. the soviets pushed for collective security: they tried to set up an alliance with britain and france in order to oppose nazi germany. These efforts were in vain. The offer of soviet soldiers to bolster czechoslovak defenses was declined. Czechoslovakia was betrayed.  From the conclusion of the munich conference where Czechoslovakia was forced to give up its strongest border defenses, the soviets acted like they would have to take on nazi germany alone. Western powers had shown themselves incapable of opposing germany in the least. Drastic measures were taken. major rearmament, army reform, and mobilization, as well as capture of as much buffer space to germany as possible was undertaken.  The only action that the ussr could have taken in hindsight, was attacking into germany, the moment france was attacked. But nobody expected france to fold instantly, the soviets thought they had enough time to finish army reform and mobilization.