Iyasu was a grandson of Menelik II of Ethiopia via Menelik's eldest daughter, and was proclaimed heir apparent in 1909.
As ruler, he continued Menelik's program of modernization, including the establishment of the first police force in Addis Ababa, but he was accused of being a Muslim and deposed 27 September 1916 in favor of his aunt Zauditu.
He evaded capture however, and spent five years at large in the countryside before being taken into custody by Gugsa Araya on 11 January 1921. In 1931 he escaped from imprisonment at Fikke, but was shortly recaptured.
Iyasu seems to have had at least thirteen wives, and seven children.