What linked east African city states such as Mombasa Mogadishu and Zanzibar?

East African city-states like Mombasa, Mogadishu, and Zanzibar were linked primarily through trade, particularly in spices, gold, and ivory, facilitated by the Indian ocean trade routes. They served as key ports for merchants from various cultures, including Arab, Persian, Indian, and later European traders. The shared Islamic culture and language, along with intermarriage and cultural exchanges among the diverse populations, further connected these city-states. This network contributed to their economic prosperity and cultural development during the medieval period.