TOPSHOT - A US Army serviceman sits at the tailgate of an helicopter carrying US Defence Secretary, after leaving the Resolute Support headquarters, in the Afghan capital Kabul on April 24, 2017.
US Defence Secretary Jim Mattis arrived in Afghanistan on an unannounced visit April 24, an American defence official confirmed, hours after his Afghan counterpart resigned over a deadly Taliban attack. Mattis, making his first visit to Afghanistan as Pentagon chief, was due to meet top officials including President Ashraf Ghani less than two weeks after the US dropped its largest non-nuclear bomb on Islamic State hideouts in the country's east.  / AFP PHOTO / X90178 / JONATHAN ERNST        (Photo credit should read JONATHAN ERNST/AFP/Getty Images)