The Iran nuclear program's Arak heavy water reactor. Photo: Nanking2012/Wikimedia Commons.

New York Times – President Obama’s decision to engage in a lengthy battle to defeat the Islamic State in Iraq and Syria reorders the global priorities of his final years in office. The mystery is whether it will deprive him of the legacy he had once hoped would define his second term, or enhance it instead.

Until now, Mr. Obama’s No. 1 priority in the Middle East has been clear: preventing Iran from obtaining a nuclear weapon.

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