Complex sentence: Most vessels were stationed in the port of Massawa in the Italian colony of Eritrea; lesser port facilities existed at Mogadishu in Italian Somaliland and Assab in Eritrea.
Split into simpler sentences: Most vessels were stationed in the port of Massawa in the Italian colony of Eritrea. However, lesser port facilities existed at Mogadishu in Italian Somaliland and also at Assab in Eritrea.