MOUNT BENTAL, Golan Heights—This mountaintop on the edge of the Israeli-controlled Golan Heights offers a unique vantage point into how the complexities of the Syrian war raging in the plains below are increasingly straining Israel’s ties with the U.S.

To the south of this overlook, from which United Nations and Israeli officers observe the fighting, are the positions of the Nusra Front, the Syrian branch of al Qaeda that the U.S. has targeted with airstrikes.

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