Complex sentence: By nightfall the Guards Armoured Division had established itself in the Eindhoven area however transport columns were jammed in the packed streets of the town and were subjected to German aerial bombardment during the night.
Split into simpler sentences: By nightfall the Guards Armoured Division had established itself in the Eindhoven area. However, transport columns were jammed in the packed streets of the town and were subjected to German aerial bombardment during the night.