Complex sentence: Despite the diplomatic conditions, the Poles dispatched Haller's Army against the Ukrainians first, instead of the Bolsheviks; this was done in order to break the stalemate in eastern Galicia.
Split into simpler sentences: Despite the diplomatic conditions, the Poles dispatched Haller's Army against the Ukrainians first, instead of the Bolsheviks. The tactical initiative was done in order to break the stalemate in eastern Galicia.