Complex sentence: In 550, together with his younger brother Justinian, he joined their father in his expedition against Ostrogoth Italy, but Germanus died suddenly in the autumn of 550, before the army had left the Balkans, where it was assembling.
Split into simpler sentences: In 550, together with his younger brother Justinian, he joined their father in his expedition against Ostrogoth Italy. Germanus however died suddenly in autumn 550, before the army had left the Balkans, where it was assembling.