Serbian protesters hold a banner that reads: "Serbia-Russia, we don't need the European Commission" on March 21 in Belgrade. The marchers were from a Serbian nationalist organization opposed to the government, which has pursued closer ties with Western Europe. Darko Vojinovic/AP hide caption

itoggle caption Darko Vojinovic/AP

A soldier in the Russian army posed, rifle in hand, for a snapshot at a battlefield checkpoint. Simon Ostrovsky, at right, located the same spot in Vuhlehirsk, in Ukraine's Donetsk region. VICE News hide caption

itoggle caption VICE News

Unmanned observation towers, funded by the European Union, have sprouted recently along Poland's border with Russia. This one is located outside the sleepy Polish border village of Parkoszewo. Soraya Sarhaddi Nelson/NPR hide caption

itoggle caption Soraya Sarhaddi Nelson/NPR

U.S. Bradley fighting vehicles take part in a joint exercise with Georgia at a military base near Tbilisi. Bradleys would be deployed to NATO member states in Eastern Europe and the Baltics if a Pentagon proposal is approved. Zurab Kurtsikidze/EPA/Landov hide caption

itoggle caption Zurab Kurtsikidze/EPA/Landov

Russian President Vladimir Putin met Wednesday with Italian officials and Pope Francis, as the U.S. sought to encourage the Vatican to join the West in condemning Moscow's actions in Ukraine. Luca Bruno/AP hide caption

itoggle caption Luca Bruno/AP

President Obama drinks a beer as he sits between men dressed in traditional Bavarian clothes during a visit to the village of Kruen, southern Germany, on Sunday, prior to the G-7 summit. Markus Schreiber/AP hide caption

itoggle caption Markus Schreiber/AP

Visitors check out the Soviet-era metro cars exhibited at the Partizanskaya subway station in Moscow, as part of festivities marking the subway system's 80th anniversary. Pavel Golovkin/AP hide caption

itoggle caption Pavel Golovkin/AP

A Proton-M rocket shown in 2013. The same type of rocket malfunctioned in mid-flight on Saturday and crashed over Siberia carrying a Mexican communications satellite. PHOTO ITAR-TASS/ITAR-TASS/Landov hide caption

itoggle caption PHOTO ITAR-TASS/ITAR-TASS/Landov

The new Russian Armata T-14 tank shown during the Victory Day military parade in the Red Square in Moscow, on Saturday. Yuri Kochetkov/EPA/Landov hide caption

itoggle caption Yuri Kochetkov/EPA/Landov

Russian military personnel march in Moscow's Red Square during a rehearsal Thursday for the Victory Day military parade that will take place Saturday to celebrate the 70th anniversary of the victory over Nazi Germany in World War II. Ivan Sekretarev/AP hide caption

itoggle caption Ivan Sekretarev/AP

Helicopter belonging to the Netherlands participates in NATO's Dynamic Mongoose anti-submarine exercise in the North Sea, off the coast of Norway, on May 4, 2015. MARIT HOMMEDAL/AFP/Getty Images hide caption

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A Russian launch vehicle carrying the Progress M-27M cargo ship lifts off from the Baikonur cosmodrome in Kazakhstan on Tuesday. Fears mounted Wednesday that the unmanned cargo capsule was lost and may plunge back to Earth as ground control failed to gain control of the orbiting ship for a second day in a row. Roscosmos /EPA /Landov hide caption

itoggle caption Roscosmos /EPA /Landov

President Obama speaks beside Russian President Dmitry Medvedev after signing New START documents in 2010. Now five years old, that treaty has taken on renewed relevance in light of the framework nuclear deal between the U.S. and Iran. Joe Klamar/AFP/Getty Images hide caption

itoggle caption Joe Klamar/AFP/Getty Images

A Russian Emergencies Ministry ship is seen through the window of a helicopter during a rescue operation after the Russian trawler Dalniy Vostok sank off the coast of Kamchatka, in the Sea of Okhotsk, on Thursday. Reuters /Landov hide caption

itoggle caption Reuters /Landov

Cars drive past the Kremlin along the Moscow River last December. Foreign automakers had been ramping up production in Russia, but the country's economic woes have caused car sales to drop sharply. Several foreign automakers have cut back production, and General Motors is pulling out of Russia. Alexander Zemlianichenko/AP hide caption

itoggle caption Alexander Zemlianichenko/AP