Complex sentence: Fulvius and his army had had a rather easy time in Apulia, and the Romans were unaware of Hannibal's presence until he was within the immediate area of Herdonia.
Split into simpler sentences: Fulvius and his army has had a rather easy time in Apulia. Fulvius was unaware of Hannibal's presence until he was within the immediate area of Herdonia.