Rand Paul in Reuters

On War & Peace: Arming Syrian rebels wades into another civil war

"Intervention is a mistake. Intervention when both sides are evil is a mistake. Intervention that destabilizes the Middle East is a mistake. And yet, here we are again, wading into a civil war," Paul said.

His doubts ran contrary to the thinking of Rubio, who advocated an aggressive response, saying the threat should have been addressed earlier. "If we do not confront and defeat ISIL now we will have to do so later, and it will take a lot longer, be a lot costlier, and be more painful," Rubio said, using an acronym for Islamic State. "If we fail to approve this, the nations of that region will say America is not truly engaged."