Tactics reminiscent of the early American frontier days are now being used in Vietnam. Lieutenant Commander Donald D. Sheppard, UBN, of Coronado, California, aims a flaming arrow at a bamboo hut concealing a fortified Viet Cong bunker on the banks of the Bassac River, Vietnam on December 8, 1967. (Photo by AP Photo)

The head of a mountain ram is attached to a wooden column at the site used for shamans' rituals in the Aldyn Bulak area on the bank of the Yenisei River during sunset outside the village of Elegest, Tuva region, Southern Siberia, Russia, October 7, 2015. The region is inhabited by Tuvans, historically cattle-herding nomads, who nowadays practise two main confessions – Buddhism and Shamanism. (Photo by Ilya Naymushin/Reuters)

A 20 metre high spiral staircase in a tower used as an emergency exit, is seen inside a Federal Reserve bank (Bundesbank) bunker, prior to the bunker's official opening to the public in Cochem, Germany, March 18, 2016. West Germany's Central Bank (Deutsche Bundesbank) stored some 20 billion German marks of emergency notes in two underground bunkers, one in Frankfurt the other in Cochem, between 1964-1988 during the cold war. (Photo by Kai Pfaffenbach/Reuters)

Blind and visually impaired Palestinian students walk down the stairs at a school, where they are taught English through song and music, at a school in the West Bank city of Hebron March 2, 2016. Palestinian students at a school for the blind in the West Bank are learning English through song, a welcome departure from using braille and memorising grammar rules. While students are delighted with the change, some parents in the religiously conservative town of Hebron are concerned that using music in the classroom jars with Islamic tradition. (Photo by Ammar Awad/Reuters)

5-year-old Rina Kumari rubs her eye while cracking stones on the banks of Mahananda river in Siliguri, northeast India, March 5, 2005. Over 400 million people in India live below the internationally agreed poverty line (living on less than US $1 per day). According to estimates, several hundred thousand children work as labourers and beg on the streets in India. (Photo by Desmond Boylan/Reuters)

A masked Palestinian uses a board to protect himself during clashes with Israeli forces which occurred shortly before Palestinian leader Mahmoud Abbas' speech to the the United Nations General Assembly, on September 23, 2011 in Qalandia, West Bank. (Photo by Ilia Yefimovich/Getty Images)

Police in riot gear hold back demonstrators against U.S. Republican presidential candidate Donald Trump outside the Hyatt hotel where Trump is set to speak at the California GOP convention in Burlingame, California, U.S., April 29, 2016. (Photo by Noah Berger/Reuters)

A 14 year-old Myanmar girl carries three bags of powdered-limestone to load in to a boat on the bank of Ayeyarwaddy River, on International Women's Day in Mandalay, Myanmar, Tuesday, March 8, 2016. Migrant workers living along Ayeyarwaddy riverbank earn bout 5000 Kyats (US Dollar 4) a day for loading and unloading goods. (Photro by Hkun Lat/AP Photo)