No better example of this confused state of affairs exists than the current fighting in Yemen. There, Houthi rebels backed by Iran are attempting to wrest control of the country from forces loyal to ousted Yemeni President Abd Rabbuh Mansur Hadi. Mr. Hadi is a U.S. ally who is also backed by Saudi Arabia, a bitter rival of Iran. But this month, after Saudi Arabia launched airstrikes against rebel positions in Yemen, the U.S. found itself in the awkward position of having to ask the Saudis to back off because the bombing was creating a humanitarian disaster among civilians trapped by the fighting. In effect it was asking Saudi Arabia, an ally, to stop fighting Iran, an adversary, even though both the U.S. and the Saudis want to limit Tehran's influence in the region.