A man holding a tray of belongings wades through a road at an area flooded by the Omoigawa river, caused by typhoon Etau in Oyama, Tochigi prefecture, Japan, in this photo taken by Kyodo September 10, 2015. (Photo by Reuters/Kyodo News)

An Egyptian army soldier stands guard near debris from a Russian airliner which crashed at the Hassana area in Arish city, north Egypt, November 1, 2015. Russia has grounded Airbus A321 jets flown by the Kogalymavia airline, Interfax news agency reported on Sunday, after one of its fleet crashed in Egypt's Sinai Peninsula, killing all 224 people on board. (Photo by Mohamed Abd El Ghany/Reuters)

Pfc. Sebastian Rodriguez, machine gunner, Weapons Platoon, Lima Company, 3rd Battalion, 3rd Marine Regiment, Marine Rotational Force – Darwin, fires an M240 machine gun during a night squad-attack exercise, here, May 22, 2013. (Photo by Sgt. Sarah Fiocco/U.S. Marines)

Two men ride a motorcycle away from a fire in Athens on Friday, July 17, 2015. Greek firefighters battled large brush and forest fires on the outskirts of Athens and in the country's southern Peloponnese region Friday, where flames forced the evacuation of at least three villages and two summer camps. (Photo by Giorgos Bamboukos/InTime News via AP Photo)

This Sunday, September 7, 2014 photo provided by Rachel Kirk shows smoke from a fire rising above Little Yosemite Valley near Yosemite National Park, Calif. (Photo by Rachel Kirk/AP Photo)

Sukhoi Su-30SM jet fighters of the Sokoly Rossii (Falcons of Russia) aerobatic team fly in formation during the International Army Games 2016, in Dubrovichi outside Ryazan, Russia, August 5, 2016. (Photo by Maxim Shemetov/Reuters)

Medic James E. Callahan of Pittsfield, Mass., gives mouth-to-mouth resuscitation to a dying soldier in war zone D, about 50 miles northeast of Saigon, June 17, 1967. Thirty-one men of the 1st Infantry Division were reported killed in the guerrilla ambush, with more than 100 wounded. (Photo by Henri Huet/AP Photo)

Ammunition airlift into besieged Khe Sanh, Operation Pegasus, April 1968. (Photo by Larry Burrows/AP Photo)