Complex sentence: An attack on the German 2nd Army further north threatened to bring about an encirclement; although the German 2nd Army managed to escape, it was forced to retreat and by 5 February troops of the Voronezh Front were approaching Kursk and Kharkov.
Split into simpler sentences: An attack on the German 2nd Army further north threatened to bring about an encirclement of that army as well. By 5 February 1943, troops of the Voronezh Front were approaching Kursk and Kharkov.