Members of the Shiite Huthi movement sit on a pick up truck mounted with a machine gun at a checkpoint in the Yemeni capital Sanaa on January 18, 2015. Shiite militiamen in control of Yemen’s capital seized President Abdrabuh Mansur Hadi’s chief of staff on January 17, 2015 in a new challenge to his leadership of the violence-plagued country. AFP PHOTO / MOHAMMED HUWAIS