Russian soldiers write home while serving on the Eastern Front during World War I, circa 1915. (Photo by Hulton Archive/Getty Images)

An Indian soldier from the international peace keeping force (IPKF) instructs young Sri Lankan recruits in shooting, part of the training given to the citizen's volunteer force in the North-Eastern Sri Lankan city of Batticaloa, September 28, 1989. (Photo by Barbara Walton/AP Photo)

Londoners sleep on the platform and on the train tracks at Aldwych Underground station,London, during heavy all night Nazi bombing raids, October 8, 1940. (Photo by AP Photo)

Angela Ponce, 24, (R) gets help from a fellow contestant getting dressed to compete in the "Miss World Spain" pageant in Estepona, southern Spain, October 25, 2015. Ponce, the first openly transsexual woman to compete to represent Spain at the Miss World pageant, was eliminated in the first knockout round. But Ponce already feels like a winner, she said, because her participation has brought visibility for the transgender community. "We need to educate society for diversity", Ponce said. (Photo by Susana Vera/Reuters)

A dead wild boar is seen during a hunt in Castell'Azzara, Tuscany, central Italy, October 23, 2015. Extinct across much of the country by the end of the 1800s, the number of wild boar in Italy has almost doubled over the past decade and there are now about a million roaming the country, environmental and agricultural associations say. (Photo by Max Rossi/Reuters)

Pakistani street performers sit around fire waiting for customers on a chilly evening in Rawalpindi, Pakistan, Wednesday, November 11, 2015. Some parts of Pakistan are facing a harsh winter. (Photo by B. K. Bangash/AP Photo)

According to the U.S. government, Moldova, one of the poorest countries in Europe, depends on about $1.6 billion annually sent back from the roughly one million Moldovans who left for work in in Europe, Russia, and other former Soviet Bloc countries. Photographer Myriam Meloni went to Moldova to document what she refers to as “social orphans” – children whose parents have emigrated to another country in search of a job and a better future for their families. Here: Lulia is seen washing dishes in her grandmother's house, where she lives. (Photo by Myriam Meloni)

An orangutan named “Pacquiao” dressed in a Santa Claus costume reacts as he joins an “Animal Christmas Party” at the Malabon zoo in suburban Malabon, north of Manila, Philippines Monday, December 21, 2015. The Malabon Zoo is one of the largest private collections of exotic and endemic animals in the Philippines. (Photo by Aaron Favila/AP Photo)