Black smoke rises from the spot where a Ukrainian army helicopter was shot down outside Slovyansk, Ukraine, on Thursday. Rebels shot the craft down amid heavy fighting around the eastern city. Alexander Zemlianichenko/AP hide caption

itoggle caption Alexander Zemlianichenko/AP

In his commencement address to the Military Academy at West Point Wednesday, President Obama condemned isolationism but spent more time outlining the hazards of intervention. Susan Walsh/AP hide caption

itoggle caption Susan Walsh/AP

Coal miners rally in Donetsk, Ukraine, Wednesday. The miners have gone on strike to demand Ukrainian troops and other forces leave the region, where fighting has left dozens dead this week. Ivan Sekretarev/AP hide caption

itoggle caption Ivan Sekretarev/AP

A pro-Russian fighter takes position behind a car as a truck full of rebel fighters heads toward a battle with Ukrainian forces near the airport in Donetsk Monday. The rebels say more than 30 of their number were killed in the violence. Fabio Bucciarelli/AFP/Getty Images hide caption

itoggle caption Fabio Bucciarelli/AFP/Getty Images