A British policewoman chasing after a group of naked street boys by the Serpentine in Hyde Park, London. (Photo by Reg Speller/Getty Images). 1926

Mounted cop in action on Tremont Street in Boston, Massachusetts, 1920 – 1929 (approximate). (Photo by Leslie Jones)

A member of the Fuerza Civil (Civil Force) police unit takes part in a simulated crime situation during a media presentation to show the police model that the federal government wants for the rest of the country, at the police academy in Monterrey December 17, 2014. Fuerza Civil, a tactical team of the police unit trained by the army, was created by the Nuevo Leon government in 2011 to curb down corruption and infiltration by drug gangs in the police corps, local media reported. Promising a new law to stop the infiltration of local governments by organized crime, President Enrique Pena Nieto pledged to reform the penal system and send an proposal to Congress to unify multi-layered police forces in Mexico's 31 states. (Photo by Daniel Becerril/Reuters)

A woman reacts while walking among the ruins of damaged buildings following heavy fighting between government troops and Kurdish fighters, on March 2, 2016 in the southeastern Turkey Kurdish town of Cizre, near the border with Syria and Iraq. Thousands in Turkey's Kurdish-majority town of Cizre started returning to their homes today after authorities partially lifted a curfew in place since December for a controversial military operation to root out separatist rebels. (Photo by Yasin Akgül/AFP Photo)

A member of the Philippine National Police stands guard as he detains people as part of the “Rid the Streets Of Drinkers and Youth” operation on a main road in Las Pinas city, metro Manila, Philippines June 1, 2016. (Photo by Romeo Ranoco/Reuters)

A member of a female grappling team from Qinghai Province armed police undergoes dagger exercise on August 8, 2006 in Xining of Qinghai Province, China. The female grappling team, established in May 2006, has 40 women soldiers aged 18 to 21. The training program includes grappling, boxing, dagger exercise and shooting. (Photo by China Photos). P.S. All pictures are presented in high resolution.

Egyptian riot police charge towards protesters near Egypt's Interior Ministry, as violent demonstrations continued into their second day on February 3, 2012 in central Cairo, Egypt. (Photo by Ed Giles/Getty Images)

A woman shouts asking for help during an eviction in Rio de Janeiro, Brazil, Friday, April 11, 2014. Squatters in Rio de Janeiro are clashing with police after a Brazilian court ordered that 5,000 people be evicted from abandoned buildings of a telecommunications company. Officers have used tear gas and stun grenades to try to disperse the families. (Photo by Silvia Izquierdo/AP Photo)