Yemen knot

U.S. finds itself on both sides at once in Middle East

The battle for dominance in the Middle East draws on ancient enmity between the Shiite and Sunni branches of Islam, but what drives it is a thoroughly modern struggle for power between Iran and the Arab monarchies led by Saudi Arabia. Now the United States, which has generally sought to gloss over Sunni versus Shiite conflicts, has been pulled into the tumult as the fight plays out on battlefields along a 2,000-mile arc from northern Syria through Iraq to Yemen.U.S. forces were on both sides simultaneously Thursday.