Complex sentence: Sufficient information had been gathered on the evening of 14 December to tell that the German battlecruiser squadron would shortly be leaving port but the information did not suggest that all of the German fleet might be involved.
Split into simpler sentences: Sufficient information had been gathered on the evening of 14 December to tell that the German battlecruiser squadron would shortly be leaving port. However, the information did not suggest that the whole German fleet might be involved.