A young arab boy, armed with a rifle and a knife, in the Aden Protectorate near Yemen. (Photo by Richards/Fox Photos/Getty Images). February 1938

An Aden civilian crouching in terror as British soldiers threaten him during Arabian demonstrations in Crater. (Photo by Express Newspapers/Getty Images). 1967

Colonel Roscoe Turner, the pilot of an American Boeing plane, showing his wife a model of the plane, at the airfield in Mildenhall. (Photo by R. Wesley/Fox Photos/Getty Images). 19th October 1934

Pro-government fighters stand next to a tank destroyed during recent fighting in Yemen's southwestern city of Taiz March 14, 2016. (Photo by Anees Mahyoub/Reuters)

A protester clashes with a police officer in Athens' central Syntagma (Constitution) Square in this June 15, 2011 file photo. Greece triggered the regional financial crisis in 2009 when a far higher budget deficit than previously calculated emerged. The collapse of talks with creditors in Paris last November set off a month-long sequence of events leading to elections this week and proving Greece is still the region's weak link. The vote is expected to be won by Syriza, a far-left party opposed to the bailout, worrying investors and creditors alike. (Photo by Yannis Behrakis/Reuters)

Egyptian bootblacks cleaning a European's shoes in Cairo. (Photo by Hulton Archive/Getty Images). Circa 1870

Guests on the terrace of Shepheard's Hotel, Cairo, circa 1940. (Photo by Hulton Archive/Getty Images)

Children sit on a bed in a flooded house following heavy rain in a village in Yemen's Red Sea province of Houdieda April 15, 2016. (Photo by Abduljabbar Zeyad/Reuters)