Complex sentence: In the third phase (1550-1100 BC) the city was largest and was protected by strong fortification C.Renfrew and M.Wagstaff, An Island Polity: the Archaeology of Exploitation of Melos, 1982.
Split into simpler sentences: In the third phase (1550-1100 BC) the city was at its largest and was protected by strong fortification. C. Renfrew and M. Wagstaff, "An Island Polity: the Archaeology of Exploitation of Melos", 1982.