Russian President Vladimir Putin as he answered questions on national TV Thursday in Moscow. Alexey Nikolsky/RIO Novosti/Kremlin pool/EPA/Landov hide caption

itoggle caption Alexey Nikolsky/RIO Novosti/Kremlin pool/EPA/Landov

A Russian armored vehicle on the road between Simferopol and Sevastopol in Crimea earlier this month. Russia annexed the region two weeks ago. Other Russian forces, across the border from Ukraine, may pull back in coming days. Viktor Drachev/AFP/Getty Images hide caption

itoggle caption Viktor Drachev/AFP/Getty Images

President Obama, accompanied by Dutch Prime Minister Mark Rutte, speaks during their joint news conference at the conclusion of the Nuclear Security Summit in The Hague on Tuesday. Pablo Martinez Monsivais/AP hide caption

itoggle caption Pablo Martinez Monsivais/AP

Armed men stood atop a chimney near Ukraine's naval headquarters in Sevastopol, Crimea, on Wednesday. They raised Russian flags after taking over much of the facility. Vasily Fedosenko /Reuters /Landov hide caption

itoggle caption Vasily Fedosenko /Reuters /Landov

A masked man, believed to be a Russian soldier, holds a Crimean flag as members of a pro-Russian self-defense unit stand in formation Monday in the regional capital of Simferopol. Vasily Fedosenko /Reuters /Landov hide caption

itoggle caption Vasily Fedosenko /Reuters /Landov

Troops under Russian command scream orders to turn back before firing warning shots at the Belbek airbase in Crimea. The troops were reacting to a large group of unarmed Ukrainian troops who approached them. Sean Gallup/Getty Images hide caption

itoggle caption Sean Gallup/Getty Images

Though some conservatives said President Obama's alleged weakness led to Russian President Vladimir Putin's Ukraine invasion, reaction didn't follow the usual partisan lines. Mikhail Klimentyev/AP hide caption

itoggle caption Mikhail Klimentyev/AP

Armed men in military uniform, believed to be Russian soldiers, were outside the territory of a Ukrainian military unit in Bakhchisaray, on the Crimean Peninsula, on Monday. Maxim Shipenkov/EPA/LANDOV hide caption

itoggle caption Maxim Shipenkov/EPA/LANDOV

A soldier in an unmarked uniform, but believed to be from the Russian army, stands outside one of the Ukrainian military bases in Crimea that have been surrounded by Russian forces. Ukrainian guards look on from inside the base. David Mdzinarishvili/Reuters/Landov hide caption

itoggle caption David Mdzinarishvili/Reuters/Landov