Left Unity is our motto, but when unity is put into practice it can be extremely messy. The Left in the civil war was made up of many revolutionary and popular organisations, which cooperated to an extent but were divided by their divergent goals and tactics.
What are your answers for finding ways for multiple left factions to act with unity in times of crisis?
The most important thing would be getting France to open border for transit of Soviet military aid. Even three-month opening in the spring of 1938 allowed Republicans to rebuild their forces in Catalonia after Aragón disaster, and constant stream of heavy armaments through the safe route would let Republicans to achieve superiority over the fascists.