THE CHRISTIAN/SHI'A ALLIANCE:

Iranian strategy in Yemen is aimed at deterring Saudi influence in the region as part of an ongoing battle for regional dominance. Iran is carrying out a similar campaign in Syria, where it supports the Bashar al Assad regime to counter the Saudi-backed opposition and rebel groups.

Michael Rubin, a resident scholar on the Middle East at the American Enterprise Institute, said U.S. inaction has bolstered the Houthis and their Iranian backers. He said this effect was on display when Houthi rebels captured Yemen's capital of Sanaa in 2015.

"After a decade of receiving reward after defiance, Tehran calculates it faces no risk of retaliation for its aggression," Rubin told the Washington Free Beacon. "The Revolutionary Guard has defined the Eastern Mediterranean and the Gulf of Aden as its strategic boundaries and it remains determined to follow up its rhetoric with action."

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