In the sixteenth century, walls built around the city of Harar during the reign of Emir Nur helped preserve Harari identity from being assimilated by the Oromo.[12] Harari colonies in the middle of the seaboard and Harar were also assimilated by Somalis putting the Sultanate of Harar under duress.[13] Hararis confined in the walled city became the last remnants of a once large ethnic group that inhabited the region.[14][15] According to Ulrich Braukämper, Harla-Harari semitic group were most likely active in the region prior to the Adal Sultanate's Islamic invasion of Ethiopia.