From the beginning of the 17th century Adel suffered greatly from the ravages of pagan Galla tribes, and Harrar sank to the position of an amirate of little importance.
In the region of Somaliland, now the western part of the British protectorate of that name, the Arabs established the Moslem state of Adel or Zaila, with their capital at Zaila on the Gulf of Aden.
In the 13th century the sultans of Adel enjoyed great power.
Von Brandenburg gegen den Adel (1889); J.
Baldwin, The Scutage and Knight Service in England (Chicago, 1897); Rudolf Gneist, Adel and Ritterschaft in England (1853); and F.
Des deutschen Adels (2nd ed., Waldenburg, 1851); von Maurer, Uber das Wesen des dltesten Adds der deutschen Stdmme (Munich, 1846); Rose, Der Adel Deutschlands and seine Stellung im deutschen Reich (Berlin, 1883); G.