Complex sentence: When the Germans began to expand their bridgehead at Barcs, the rebel Croat troops at Bjelovar made contact with them, and the 4th Army began to withdraw southwards on 9 April.
Split into simpler sentences: When the Germans began to expand their bridgehead at Barcs, the rebel Croat troops at Bjelovar made contact with them. The 4th Army began to withdraw southwards on 9 April.