Sunday brought the latest terrorist attack in America, the largest mass shooting in U.S. history, with all its attendant tragedy. Words cannot adequately describe the horror that engulfed the scene of this massacre, caused by one Omar Mir Seddique Mateen.

Beyond the human cost, however, also lies the tragedy that Barack Obama, speaking even as it became clear that the murderer was a radical Islamic terrorist, is still unable or unwilling to draw the appropriate conclusions. The president’s remarks omitted any linkages between the cold-blooded murders, the terrorist’s ideology, and the broader international threat that motivated the Orlando killer and perhaps others yet unknown.

We will, in the coming days, doubtless hear that the terrorist was a lone wolf, that he did not belong to any known terrorist organization, that there are no wider threats. In particular, those who are blind to the terrorist threat will downplay even the incontrovertible fact that Mateen pledged loyalty to ISIS as he committed his murders.

Two critical conclusions follow immediately from Sunday’s tragic reality, one with immediate implications for our domestic safety, and one for conducting the broader international war against terrorism.

The United States must urgently discard the fiction that we pay no price for not pursuing international terrorists vigorously and relentlessly.

First, the number of true “lone wolf” terrorists is infinitesimal. The implications of that phrase, namely that terrorism is not a widespread and still-growing phenomenon, are profoundly impairing our ability to protect innocent civilians. Terrorists like Mateen are not “one offs” who emerge randomly, unexpectedly and inexplicably, perhaps victims of mental disorders. The evidence is now indisputable that we are confronting a far larger threat, albeit not one organized conveniently for our understanding. This threat is unmistakably ideological, as Sunday’s Orlando attack and the apparently thwarted attack in Santa Monica demonstrate.

We simply must start acknowledging that terrorists -- whether ISIS, Al Qaeda, or others -- are not structured like governments or corporations. They are not staffed with desk-bound bureaucrats in grey suits, arranged pursuant to a complex, hierarchical organization chart. They do not send memoranda to each other through a complex clearance process, with copies distributed far and wide.

Nor do they function like spy networks and subversive political movements of days gone by. They do not carry party identification cards. They do not communicate through dead drops, brush passes, invisible ink and microdots. This is not an age where FBI agents have the capacity to infiltrate the “cells” that do not exist or shadow the agents who are running the actual terrorists.

Instead, it is not just the West that has mastered digital communications and Internet social networks. The terrorists are just as good at it, for their purposes better than we are at understanding their techniques and their success. Actors like Mateen are not rigorously following a critical path chart in ISIS headquarters. Instead, it is precisely the disconnected, unpredictable timing of the terrorist attacks, not necessarily staged in advance, that adds to their devastating effect.

Second, the United States must urgently discard the fiction that we pay no price for not pursuing international terrorists vigorously and relentlessly. President Obama’s strategy against terrorist bases of operation, when it is evident at all, has been lackadaisical and offhanded. There is a clear rationale to this casualness. Obama manifestly believes that, as bad as terrorist attacks are, American “overreaction” is worse. In his view, the use of U.S. forces risks increasing the problem rather than reducing it, making us much a part of the problem as the terrorist threat itself.

This is, of course, utter nonsense. We are obviously defending ourselves from attack, not initiating it. And it is palpably our failure to defend ourselves that provides incentives for the terrorist to strike even harder. Here is where Obama’s failure to pursue the campaign against ISIS in Syria and Iraq is so damaging. A slow, casual offensive against ISIS gives the terrorists time and opportunity to encourage strikes like the one we have just seen.

There is a cost -- and a very human cost -- to allowing ISIS any respite from the full force of U.S. and allied military power. It is not cost-free to slow roll the anti-ISIS campaign, not in the Middle East, not in North Africa, and most certainly not in the United States.

While the foreign political and military complexities of obliterating ISIS are real enough, presidential resolve and determination can overcome much. Obama’s resolve and determination are AWOL.

I have long argued that the central issue of the 2016 elections should be national security. The Orlando massacre has tragically underlined that point. President Obama may not be able to acknowledge the grim reality endangering us, but the rest of us must do so. Fortunately, we will pick a new president this November, and that choice must, at all costs, be someone who does not share Obama’s failings. The winning presidential candidate will be the one whose anti-terrorism policies are the most distinguishable from Obama’s.