Russia and North Korea: what can they do for each other?

China accounts for more than 90% of North Korea's trade and has been its most dependable aid donor and diplomatic ally. But as Vladimir Putin's imminent visit to Pyongyang proves, the secluded state's behaviour is being increasingly influenced by its security and economic ties with Russia. How does Russia help North Korea? China is not the only regional power to have allegedly helped North Korea skirt UN sanctions and prevent its economy from collapsing. Last month, the US claimed Russia had been shipping refined petroleum to North Korea in quantities that reportedly exceed the limit imposed by the UN security…