Why is 9 AH called the Year of Delegations?

It is called that because delegations of Arab tribes came to the Prophet ﷺ from every direction that year, after the conquest of Mecca, the expedition to Tabuk and the conversion of Thaqif. ¹ Ibn Hisham reports, citing Abu 'Ubayda, that it was in the year nine and that it was called the year of delegations. ¹

Ibn Ishaq explains the arrival of the delegations by saying that the Arabs were waiting to see the outcome of the affair of Quraysh. Quraysh were the leaders of the people, the people of the Sacred House, the pure line of Isma'il, and the leaders of the Arabs, and they had set themselves up to fight the Prophet. When Mecca was conquered and Quraysh submitted to him, the Arabs understood that they had no power to fight him or oppose him, and they entered the religion of God in multitudes. ¹ He cites the chapter of Victory as evidence: An-Nasr 2. ¹

Among the delegations of that year in Ibn Hisham's biography are the delegation of Banu Tamim, who boasted to the Prophet with their orator and their poet and then embraced Islam; the delegation of Banu 'Amir, in which the plot of 'Amir ibn al-Tufayl and Arbad took place; Dimam ibn Tha'laba, the envoy of Banu Sa'd ibn Bakr; the delegation of 'Abd al-Qays with al-Jarud; and the delegation of Banu Hanifa, which included Musaylima. ^{2 3 4 5 6}

• Ibn Ishaq does not confine all the delegations to the year nine. Some he places in the year ten or before al-Hudaybiyya. The full list is in the entry The year of delegations.
• Later sources mention other delegations that Ibn Ishaq does not report in this part. ⁷

Readings by modern researchers of the meaning of "delegations", and of the relationship between the tribes and the emerging state, will be added from their sources.