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)

Khansa, an eight month old critically endangered Bornean orangutan shows off it's two front-teeth, at the Singapore Zoo on Thursday, January 11, 2018 in Singapore. The Singapore Zoo is active with its breeding programs as part of its wildlife preservation efforts. This is the Zoo's 46th successful orangutan birth. (Photo by Wong Maye-E/AP Photo)

In this 2017 photo provided by Simon Pierce, Jonathan Green checks on a fin-mounted satellite tag on a whale shark in the Galapagos Islands area of Ecuador. Despite typically being bigger than a double-decker bus, the elusive whale shark has only tiny, almost useless teeth. It's also one of the least understood animals in the ocean. (Photo by Simonjpierce.com via AP Photo)

People participate in the first day of Thingyan Water Festival in Naypyitaw, Myanmar on April 13, 2018. The annual water festival, known as Thingyan, features large groups of people congregating to celebrate the by splashing water and throwing powder at each other's faces as a symbol of cleansing and washing away the sins from the old year. It marks the start of the traditional New Year and is similarly celebrated in countries such as Myanmar, Thailand, Laos and Cambodia. (Photo by Hein Htet/EPA/EFE/Rex Features/Shutterstock)

A photo taken on August 21, 2017 shows girls passing in front of a building with a display of the Soviet state founder Vladimir Lenin Order in Volgograd, Russia. Volgograd Arena will host several cames of the FIFA World Cup 2018. (Photo by Mladen Antonov/AFP Photo)

A moon light illuminates the sky through the clouds over a large line of grass between some home houses in the small village of Tafalla, northern Spain, Tuesday, May 1, 2018. (Photo by Alvaro Barrientos/AP Photo)

A Sadhu or a Hindu holy man stands on the banks of the river Ganges before taking a holy dip during “Kumbh Mela”, or the Pitcher Festival, in Prayagraj, previously known as Allahabad, India, February 3, 2019. (Photo by Adnan Abidi/Reuters)

An Orthodox child is given an icy dip in a lake in celebration of Epiphan, near the village of Vorontsovka, some 20 km from the Kyrgyz capital of Bishkek, Kyrgyzstan, 19 January 2019. People believe that bathing in blessed waters during the holiday of Epiphany strengthens their spirit and body. (Photo by Igor Kovalenko/EPA/EFE)