The drop in oil prices to their lowest in two years has caught many observers off guard, coming against a backdrop of the worst violence in Iraq this decade, heightened tensions between the West and Russia, and sanctions against Iran.
But as rising supplies of North American crude and tepid demand have pushed prices below $100 a barrel, the move underlies how the shale oil revolution is creating a political and economic advantage for Washington and its Western allies.
Russia and Iran are heavily reliant on oil sales and face budget shortages at current price levels, analysts say, weakening their position when negotiating over Ukrainian sovereignty or the Iranian nuclear deal.
