Care to see what we are doing now?  "The mass murder obviously has tragic effects for those killed and wounded, and for their families, but this is not a tragedy.  It is a war crime targeting a civilian population in the course of an ongoing war, which - notwithstanding the reckless posturing by the commander-in-chief - is not close to "winding down," much less being over. ...... We cannot "end" the war by withdrawing from it; we can only lose that way."

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Defense Secretary Ash Carter happened to be scheduled to testify before Congress today. Thus, he provided the government's first reaction to the jihadist atrocity in Brussels, in which 31 are dead (the toll is expected to rise) and scores of others have been wounded. Secretary Carter called the attacks a "tragedy."

The mass murder obviously has tragic effects for those killed and wounded, and for their families, but this is not a tragedy. It is a war crime targeting a civilian population in the course ofan ongoing war, which - notwithstanding the reckless posturing by the commander-in-chief - is not close to "winding down," much less being over. It was simply shocking this morning to watch split screens. On one, we saw President Obama spend fleeting seconds on a peremptory acknowledgement of the attacks before moving on to his long, celebratory speech about how he has put the Cold War to rest in Cuba by working with "President Castro." On the other screen, Belgians chaotically fled fire and debris while emergency personnel rushed the wounded to ambulances and carried out the dead.

Our enemies are at war with us. They continue to execute acts of war, not tragedies, against us. We cannot "end" the war by withdrawing from it; we can only lose that way. We cannot prevail, or even adequately protect ourselves, without seeing the enemy plain: radical Islam - Islamic supremacists determined to impose sharia on the world, with jihadists as the pointy end of the spear, and ideological sympathizers as their support system.

Because the latest round of war crimes occurs in the context of our momentous decision about who will be the next commander-in-chief, it is worth observing that Ted Cruz, whom I support (and on whose advisory team I serve), has stressed a recognition that the enemy is radical Islam. This is not just campaign rhetoric. We know, nearly a quarter century after the 1993 World Trade Center bombing, that jihadist cells arise and thrive in ideological enclaves; that is where the radicalization, recruitment, fundraising, plotting, and injection and protection of jihadist immigrants occurs. We cannot deny reality by rationalizing that if we admit the truth we will be misunderstood as being "at war with Islam" - as in all Muslims.

What we like to think of as "radical Islam" is actually a legitimate and rabidly anti-Western interpretation of Islam that is followed by millions of Muslims. It is irrelevant to non-Muslims in the West whether theirs is a correct or incorrect construction of Muslim scripture. The remorseless fact remains that its adherents believe it - with a fervor that inspires the kinds of attacks we've seen today and have seen over and over again. Those adherents include Muslims who lack the commitment to carry out attacks themselves but nevertheless provide moral (and other) support to those who do, and who populate the Western immigrant enclaves in which the ideology thrives.

It's a welcome fact that there are other ways of interpreting Islam that do not endorse war and hostility against the West; those who offer these interpretations are our allies, and we should be encouraging them rather than turning to enemies such as the Muslim Brotherhood to help us conduct "community outreach." Still, the fact that there are pro-Western Muslims and authentically tolerant interpretations of Islam does not - and cannot be allowed to - obscure the fact that Islamic supremacism is a mainstream construction of Islam. It is not "false" Islam, or "anti-Islam." It is Islam that competes, violently, with other constructions of Islam.

It is not our job to broker the claims these competitors make regarding what is the "true Islam." It is our job to protect ourselves and our allies, and to crush the jihadist armies and cells that are prosecuting the war against us. If we do not acknowledge what the threat is and where it is coming from, we will continue to embrace the policies that empower the enemy. In a time of war, we cannot indulge a policy of mass immigration from countries where sharia supremacism is a significant presence.

With respect to Muslim immigrant communities that are already here, we must have sensible surveillance policies that identify and focus police attention on mosques and community centers that endorse anti-Western Islamic supremacism. That is not a dragnet against all Muslims; it is the arena where pro-American Muslims can step up and help us. No law-enforcement or intelligence agency wants to waste its time and resources investigating innocent people. But we have to be clear that Muslims who endorse Islamic supremacism, who want our Constitution supplanted by sharia, are on the wrong side of this war, regardless of whether they cross the line into violence.

Finally, we cannot tolerate jihadist safe havens anyplace on earth. The administration recently conceded that it has no strategy to deny the Islamic State - which has claimed responsibility for today's attack - their sanctuary in Raqqa (to say nothing of their other strongholds). Let's be clear: If ISIS is orchestrating attacks on the West from Syria and Iraq, that is an Americannational-security challenge, not just a civil war in a faraway place. American national-security problems cannot responsibly be delegated to other forces who will carry out our defense and war-fighting responsibilities for us. This is our problem.

There has not yet been a serious bombing campaign against ISIS and al-Qaeda in Syria and Iraq, and it is fair enough to say that the number of troops we may have to commit hinges on how committed we are to an intense air campaign. We should not delude ourselves, however: The jihadists are planning to attack the United States as well as Europe, and it is going to take American military commitment to destroy them - not to carry out an experiment in democracy-building, but to eradicate the threat to our nation and our allies.

A version of this piece previously appeared on National Review Online.