U.S. soldiers from the 3rd Cavalry Regiment take part in an artillery exercise on forward operating base Gamberi in the Laghman province of Afghanistan December 24, 2014. (Photo by Lucas Jackson/Reuters)

Starting on Monday, August 12, Perseid meteors will streak across the summer sky for a couple of nights, offering casual stargazers and serious nighttime photographers a chance to capture a glimpse of the annual meteor shower. Photo: Photographer David Kingham created this composite image from 23 photos on August 12, 2012. (Photo by David Kingham)

A flood-affected couple sits along a flooded roadside under a picture of Jayalalithaa Jayaram, chief minister of the southern Indian state of Tamil Nadu, in Chennai, India, December 6, 2015. (Photo by Anindito Mukherjee/Reuters)

A boy carries sugar cane through a farm on the outskirt of Zaria in Nigeria's northern state of Kaduna November 15, 2016. (Photo by Akintunde Akinleye/Reuters)

People take pictures of deer in the Phoenix Park in Dublin, Ireland December 5, 2016. (Photo by Clodagh Kilcoyne/Reuters)

India: A sweeper cleans the side of a road near a replica of the Eiffel Tower amid heavy fog in the early morning in the northern Indian city of Chandigarh January 18, 2010. (Photo by Ajay Verma/Reuters)

Filipino firemen extinguish a burning vehicle during an earthquake preparedness drill in Makati city, south of Manila, Philippines, 22 June 2016. Thousands of people participated in the Metro Manila earthquake drill to prepare residents of nearly 12 million for a feared magnitude-7.2 quake that could kill thousands and displace millions, Emerson Carlos head of the Metropolitan Manila Development Authority (MMDA) said. Philippines sits on the Pacific Ring of Fire, an area prone to seismic shifts that spark earthquakes and volcanic activity. (Photo by Francis R. Malasig/EPA)