Yemen

From the incense kingdoms of Saba and the great Marib Dam to the long Zaidi imamate, the union of two states, and a war the UN calls one of the world's worst humanitarian crises.

Yemen occupies the fertile southwestern corner of Arabia, where the ancient incense kingdoms of Saba, Qataban and Hadramawt grew wealthy on the caravan trade in frankincense and myrrh and built the celebrated Great Dam of Marib. After Islam reached the region in the 7th century, a Zaidi imamate took root in the northern highlands and endured, in varying forms, for over a thousand years, while the Ottomans and, in the south, Britain at Aden contested control of its coasts. North Yemen emerged from Ottoman rule in 1918 and South Yemen won independence from Britain in 1967; the two states merged into the Republic of Yemen on 22 May 1990. Since 2014–15 the country has been gripped by war and a humanitarian catastrophe that United Nations agencies have ranked among the gravest in the world.