The Spanish title for this film was "Arenas de Muerte", which literally translates to "Sands of Death". The Spanish poster only features a closeup of the face of Sophia Loren and her name comes above John Wayne's. She was a much bigger star in Spain than Wayne was in 1957.
Shortly before filming began John Wayne was devastated when the US sided with the Soviet Union in the Suez Crisis. He called for military action in response to the Soviet invasion of Hungary. Wayne had always had a very low opinion of the then US President Dwight D. Eisenhower, and this increased after Suez. However, he continued to publicly support Eisenhower, as he felt Adlai Stevenson--a progressive Democrat--as President would be far worse for the US and its allies.
In a documentary about British director of photography Jack Cardiff, it was said that director Henry Hathaway was not respectful to the English members of the crew--he did not, for example, like their penchant for taking breaks for tea.
The Bible text, "And they shall go into the holes of the rocks, and into the caves of the earth, for fear of the LORD, and for the glory of his majesty, when he ariseth to shake terribly the earth. / In that day a man shall cast his idols of silver, and his idols of gold, which they made each one for himself to worship, to the moles and to the bats...", is from Isaiah, chapter 2 verses 19-20.