The US and Europe have imposed increasingly deeper economic sanctions on Russia because of perceived aggression in Ukraine. Now, President Vladimir Putin is responding with sanctions of his own. Russia today banned some imports from the US and Europe and extended Edward Snowden’s permission to stay in the country for three more years. President Putin signed an oil deal with Iran — and he might prohibit western airliners from flying over Siberia. Andrew S. Weiss is Vice President for Studies at the Carnegie Endowment.