after the successful 2nd ukrainian front's kecskemét-budapest offensive (29 october 1944 – 10 december 1944) and szolnok–budapest offensive (29 october 1944 – 10 december 1944) east of balaton, the german forces south-west of the lake retreated, which aided the bulgarian advance. the bulgarian 1st army breached the first two defensive axis lines and crossed the mura river. they then assumed a defensive posture at the veliki kog-yastrebtzi line and remained there until 7 may.