At this point, readers may sense that Mr. Cruz is closer to President Obama when it comes to fighting terrorism than he lets on. His views on metadata collection are identical to those of James Clapper, the incompetent and dishonest Director of National Intelligence whom Mr. Cruz cites approvingly in his speech. He excoriates the Obama administration for hollowing out the military but fails to note that he was one of just two Republican votes (the other was Rand Paul) against the latest National Defense Authorization Act, opposition he justifies on obscure civil-liberty grounds. He cites Libya as a case study in why not to intervene in a Middle Eastern civil war. But he may also have noted that his anti-interventionist instincts precisely track those of Mr. Obama, who was reluctantly dragged into a war he led from behind.

As for Syria, Mr. Cruz insists “we do not have a side in the Syrian civil war” and endorses Israeli Prime Minister Benjamin Netanyahu’s view that nonintervention allows two evil sides to exhaust themselves in the fighting. But this is indistinguishable from Mr. Obama’s hands-off approach to the conflict, notwithstanding the administration’s flaccid efforts to arm a credible opposition and bomb ISIS.

If your aim is to bomb ISIS until the “sand glows in the dark,” you are taking a side in the conflict. Mr. Cruz knows this. If you want to destroy ISIS without strengthening the Assad regime and its backers in Tehran, you have to target the regime, too. The truth about Syria isn’t that we have no dog in the fight. It’s that we’ve got to fight two dogs. The alternative is the endless chaos in which ISIS incubates and desperate refugees come knocking on our doors.