the 57th army was the southernmost unit of the red army on the eastern front. south of the 57th army, the germans of 2nd panzer army and army group e were confronted by soviet allies—bulgarian forces in southern hungary and tito's forces in yugoslavia. an attack in these areas offered the germans the opportunities of attacking the less well equipped bulgarians and yugoslavs as well as potentially rolling up part of the soviet southern flank. thus, this region was of particular concern to soviet marshal fyodor tolbukhin, whose 3rd ukrainian front was deployed in southern hungary and which commanded both the 57th army and the bulgarian first army. (the unit south of the bulgarians was the yugoslav 3rd army which was not subordinated to 3rd ukrainian front.) alerted that a german attack south of lake balaton was imminent, marshal tolbukhin deployed additional artillery units to reinforce the 57th army and the bulgarian iii corps.