A Polish Army tank takes part in the NATO Noble Jump exercise on a training range near Swietoszow Zagan, Poland, Thursday, June 18, 2015. (AP Photo/Alik Keplicz)

Omani Tactical & Commando personnel are seen during the month-long GCC joint security exercise “Arabian Gulf Security 1” in Manama, Bahrain November 1, 2016. “Arabian Gulf Security 1” exercises will continue until mid-November with the participation of the UAE, Saudi Arabia, Oman, Qatar and Kuwait. (Photo by Hamad I. Mohammed/Reuters)

Demonstrators protest during a rally against Venezuelan President Nicolas Maduro, in Caracas on April 19, 2017. Venezuela braced for rival demonstrations Wednesday for and against President Nicolas Maduro, whose push to tighten his grip on power has triggered waves of deadly unrest that have escalated the country' s political and economic crisis. (Photo by Juan Barreto/AFP Photo)

Moscow riot policemen detain an activist during an unauthorized protest anti-Putin opposition rally to defend Article, 31 of the Russian Constitution which guarantees the right of assembly, in Triumfalnaya Square in Central Moscow, Russia, on December, 31, 2011 (Photo by Konstantin Zavrazhin/Getty Images)

Photo by: Sergey A.; Source: LiveJournal

Police take part in a role play exercise as they clear a protest on top of a train during training on March 6, 2012 in Oxenhope, England. A new team of specialist officers set up to deal with searches and policing at a height, such as on top of a train, undergo training exercise in Oxenhope, West Yorkshire. (Photo by Bethany Clarke/Getty Images)

Palestinian militants from al-Husine brigade loyal to Fatah movement exits from a tunnel during during a military-style exercise graduation ceremony in Khan Younis in the southern Gaza Strip, September 20, 2015. (Photo by Suhaib Salem/Reuters)

Anti-Heathrow expansion activists walk through the “Grow Heathrow” protest camp in the village of Sipson near to Heathrow Airport, west London Britain December 7, 2015. (Photo by Peter Nicholls/Reuters)

Activists and supporters of Ukrainian nationalist groups light flares during a rally to mark the third anniversary of the Euromaidan Revolution in downtown Kiev, Ukraine, 21 November 2016. About one thousand activists took park in the rally during which they burned tires on the Independence Square, destroyed the Russian bank Sberbank and broke windows in the office of a Ukrainian politician Viktor Medvedchuk, according to Ukrainian media. (Photo by Roman Pilipey/EPA)