Complex sentence: Under the leadership of Vershigora 1st Ukrainian partisan division raided western Belarus and eastern Poland harassing the German rear and on July 3,1944 joined the regular Soviet army that was fighting to liberate Belarus.
Split into simpler sentences: Under the leadership of Vershigora, the 1st Ukrainian partisan division raided western Belarus and eastern Poland, harassing the German rear. On July 3,1944 they joined the regular Soviet army that was fighting to liberate Belarus.