Complex sentence: Not even the return of Belisarius could stem the Ostrogothic tide: by 550, the East Romans were left with a handful of coastal strongholds in the mainland, and in the spring of that year, Totila even invaded Sicily, the Romans' strategic base.
Split into simpler sentences: Not even the return of Belisarius could stem the Ostrogothic tide. By 550, the East Romans were left with a handful of coastal strongholds in the mainland, and in the spring of that year, Totila even invaded Sicily, the Romans' strategic base.