This chapter begins with a lengthy examination of Siena’s greatest military triumph, its victory over Florence at the battle of Montaperti in 1260, as well as the aftermath of the event. Although Siena’s victory was overturned by Florence less than a decade later, stories from Montaperti would become central to Siena’s image and identity in the coming centuries. This chapter also examines the high point of Sienese civilization, under the government of the Nine, who were responsible for many of the city’s most historic monuments and works of art.