Complex sentence: As part of Operation Abigail Rachel, the "first deliberate terror raid" on Germany took place on 16 December, although with poor effect even though one hundred tonnes of explosives and 14,000 incendiaries were dropped on Mannheim.
Split into simpler sentences: As part of Operation Abigail Rachel, the "first deliberate terror raid" on Germany took place on 16 December. Although of poor effect, the raiders dropped one hundred tonnes of explosives and 14,000 incendiaries on Mannheim.