Crete remained a province of the Roman Empire until a.d. 395, with Gertis as its capital.
Gertis was the capital of Crete when it was a province of the Roman Empire. 
mnli hypothesis: Gertis was the capital of Crete when it was a province of the Roman Empire.  premise: Crete remained a province of the Roman Empire until a.d. 395, with Gertis as its capital.