Complex sentence: He ordered Steiner to attack the northern flank of the huge salient created by the 1st Belorussian Front's breakout while the Ninth Army which had been pushed south of the salient was to attack north in a pincer attack.
Split into simpler sentences: He ordered Steiner to attack the northern flank of the huge salient created by the 1st Belorussian Front's breakout. Simultaneously the Ninth Army, which had been pushed south of the salient, was to attack north in a pincer attack.