A woman loyal to the Houthi movement holds a rifle as she takes part in a parade to show support to the movement in Sanaa, Yemen September 6, 2016. The Saudi-led Arab coalition launched a military campaign against the Huthis and their allies in March 2015, after the rebels closed in on Gulf-backed President Abedrabbo Mansour Hadi in his southern refuge of Aden, forcing him into exile. (Photo by Khaled Abdullah/Reuters)

Philippine Marines from the Naval Special Operations Group (NAVSOG) storm the beach to simulate an “extraction” of a kidnapped victim as they kick off a five-day amphibious military exercise at the Philippine Marines training center in Ternate, Cavite province, about 50 miles (80kms) south of Manila, Philippines Thursday, September 24, 2015. The naval exercise dubbed PAGSISIKAP 2015 is aimed at enhancing capability of their fleet and forces as well as to strengthen interoperability of the Marines. (Photo by Bullit Marquez/AP Photo)

Getting her tongue pierced was “exciting and scary” says a teen who succumbed to pressure from her best friend in Austin, Texas, February 22, 2008. This image is featured in National Geographic's exhibition “Women of Vision: National Geographic Photographers on Assignment”, on view at the Palm Beach Photographic Centre, Jan. 22 - Mar. 22, 2015. (Photo by Kitra Cahana/National Geographic)

Lindsay Mann (L) and Anabella Mowbray kiss as they take photos of themselves laying in the confetti on 7th Avenue in Times Square on New Year's Eve in New York January 1, 2015. (Photo by Carlo Allegri/Reuters)

Afghan firefighters spray water on a U.S. armoured vehicle after a suicide attack on the outskirts of Jalalabad, January 5, 2015. A suicide attacker targeted a U.S. convoy on the outskirts of Jalalabad on Monday but so far no causalities have been reported yet, provincial spokesman Ahmadzia Abdulzai said. (Photo by Reuters/Parwiz)

A swimmer reacts after finishing his competition in a pool carved into thick ice covering the Songhua River during the Harbin Ice Swimming Competition in the northern city of Harbin, Heilongjiang province January 5, 2015. The swimming competition was held on the official launch day of the Harbin International Ice and Snow Sculpture Festival. (Photo by Kim Kyung-Hoon/Reuters)

Officers react at their graduation ceremony during Iraqi Army Day anniversary celebration in Baghdad January 6, 2015. Iraqi Defence Minister Khaled al-Obeidi said on Tuesday that the Iraqi military has started rebuilding after its near total collapse last summer but that the effort is still in its initial phase. (Photo by Ahmad Mousa/Reuters)

Reenactors playing the roll of Kentucky volunteers, fighting for the United States, fire muskets during a reenactment of the Battle of New Orleans in the War of 1812, marking its bicentennial in Chalmette, Louisiana, January 10, 2015. The participants, some of whom have travelled thousands of miles to join in the event, recreated the five clashes that comprise the battle, which some historians say was key in making the British honor the terms of a peace treaty signed in late 1814. (Photo by Lee Celano/Reuters)