Complex sentence: But Roman progress was delayed by the Second Punic War: during Hannibal's invasion of Italy (218-203 B.C.), Roman control of the "pianura padana" was temporarily overthrown.
Split into simpler sentences: But Roman progress was delayed by the Second Punic War. During Hannibal's invasion of Italy (218-203 B.C.), Roman control of the "pianura padana" was temporarily overthrown.