In this March 7, 1991 file photo, a U.S. Marine patrol walks across the charred oil landscape near a burning well during perimeter security patrol near Kuwait City. Twenty five years after the first U.S. Marines swept across the border into Kuwait in the 1991 Gulf War, American forces find themselves battling the extremist Islamic State group, born out of al-Qaida, in the splintered territories of Iraq and Syria. The Arab allies that joined the 1991 coalition are fighting their own conflicts both at home and abroad, as Iran vies for greater regional power following a nuclear deal with world powers. (Photo by John Gaps III/AP Photo)

In this photo taken on Friday, July 14, 2017, a student at a paramilitary camp for children calls the rank to attention outside Kiev, Ukraine. As the deadly conflict in eastern Ukraine entered its third year, some parents in Ukraine are anxious to make sure their children are ready to fight it, instead of swimming and playing volleyball. (Photo by Efrem Lukatsky/AP Photo)

A reveller covered in tomato pulp takes part in the annual “Tomatina” festival in the eastern town of Bunol, on August 30, 2017. The iconic fiesta – which celebrates its 72nd anniversary and is billed at “the world's biggest food fight” – has become a major draw for foreigners, in particular from Britain, Japan and the United States. (Photo by Jaime Reina/AFP Photo)

South Vietnamese forces escort suspected Viet Cong officer Nguyen Van Lem (also known as Bay Lop) on a Saigon street February 1, 1968, early in the Tet Offensive. Moments later, Lem was executed by Gen. Nguyen Ngoc Loan, chief of the national police. (Photo by Eddie Adams/AP Photo)

A cat walks in front of the body of a man killed by unknown gunmen in Manila, Philippines early October 18, 2016. A sign on a cardboard found near the body reads, “Pusher Ako, Wag Tularan”, which translates to “I am a (drug) pusher, don't be like me”. (Photo by Damir Sagolj/Reuters)

Bullfighter Julian Lopez “El Juli” of Spain performs during the second bullfight of the 2011 season at the Monumental bullring on July 10, 2011 in Barcelona, Spain. This will be the last year for Bull fighting at the Monumental bullring as the parliament of Catalonia has voted to ban bullfighting as of January 1, 2012. (Photo by David Ramos/Getty Images)

Participants enjoy mud during the 14th Annual Boryeong Mud Festival at Daecheon Beach on July 16, 2011 in Boryeong, South Korea. The mud, which is believed to have beneficial effects on the skin due to its mineral content, is sourced from mud flats near Boryeong and transported to the beach by truck. (Photo by Chung Sung-Jun/Getty Images)

Yolanthe Cabau attends amfAR MILANO 2011 at La Permanente on September 23, 2011 in Milan, Italy. (Photo by Vittorio Zunino Celotto/Getty Images for amfAR)