Johannes IV (1836-1889) was an Ethiopian emperor who thwarted Egyptian, Italian, and Sudanese attempts to overrun Ethiopia and took important steps to unify the country.

Johannes IV was born in the northern Ethiopian region of Tigre with the baptismal name of Kassa. After inheriting his father's position of nobility in 1867, Kassa declared himself the independent king of Tigre. Two years later, when Takle Giorgis II, the reigning Ethiopian emperor, taunted Kassa into battle, the Tigrean king easily defeated and imprisoned the hapless emperor. Armed with the guns, ammunition, and military supplies abandoned earlier by a British expeditionary force, Kassa so built up his position that on Jan. 21, 1872, he was crowned emperor, taking the throne name of Johannes (John), after the writer of the Book of Revelation.

The opening of the Suez Canal in 1869, the Egyptian revival under Khedive Ismail, and shadowy Egyptian claims to portions of the Red...