New York City officials are already calling Tuesday’s awful attack in downtown Manhattan “an act of terror.”  Whether they are right remains to be seen; but, if so, the real test comes tomorrow, not today.  That is, today our first responders have been doing what they always do: selflessly and swiftly putting their own lives on the line to care for others.  But, tomorrow, our nation’s eyes must turn to the broader response by our leaders in Washington, and by President Trump in particular.  Terrorism is, at bottom, a strategy of provocation: It tries to get us to do to ourselves what fundamentally weaker adversaries—terrorists—cannot accomplish on their own.

To be clear, tonight we must begin to mourn the dead, and to acknowledge the tragic loss of human life that an attack like today’s inflicts.  I believe firmly that our government owes it to the American people to go to extraordinary lengths to prevent these types of deaths from terrorism, as they are terrible in themselves and, what’s more, they tend to provoke terrible chain reactions politically, economically, and diplomatically.

Tomorrow, even as our hearts remain heavy, we also must worry about how our nation’s leaders respond—because it’s that response that terrorists target, as much as the specific individuals whom terrorists horrifically kill and maim.  Terrorists seek to provoke overreaction in many forms: disproportionate military responses that vindicate terrorists’ narrative about the countries they target; fiscally draining foreign adventures that bleed target countries’ economic well-being; recriminations against allies and partners for not doing enough to counter terrorism that drive a wedge in key coalitions; rhetoric that splits people apart by ethnicity and religion; and domestic crackdowns that splinter populations and radicalize politics.

Whether an attack like Tuesday’s achieves these objectives is no longer predominantly in the terrorists’ hands—it’s in ours, or at least those of our leadership.  Will our leaders use the military as an appropriate tool in focusing on the continuing, critically important campaigns against ISIS and al-Qa’ida, or will they allow the attack to induce tactically inapt responses?  Will vile acts like these inspire the United States to get dragged into costly operations on foreign soil without clear objectives and articulable conclusions, or will they maintain a savvy, partner-centric approach where possible that allows the United States to utilize its comparative advantage while drawing on the capacities of partners on the ground?  Will such acts lead to misplaced accusations against foreign countries, whose cooperation is vital to sustainable counterterrorism, of being “soft” on terrorists and thus sow discord with those whose help we need?

And, perhaps most critically, will our leaders use Tuesday’s terrible events to unify or to divide our nation?  Cultivating resilience in the face of terrorist attacks is an indispensable part of sound counterterrorism policy.  But President Donald Trump has—bewilderingly—belittled London’s Mayor for his efforts to ensure and applaud resilience among Londoners in the wake of terrorist violence in their city.  And Trump’s initial response on Tuesday—in particular, his tweet suggesting that ISIS had “enter[ed] our country” to commit the attack—appeared to show his continuing eagerness not to reassure the American public but, instead, to use the violence to slide back closer toward his old hobbyhorse of what he urged in January, namely, “a total and complete shutdown of Muslims entering the United States.”  Back toward that end of the spectrum again, it seems—despite initial reports indicating that the suspected attacker, while an Uzbek national, has lived in the United States since 2010.  That at least appears preliminarily to make him a typical U.S.-based attacker—indeed, it makes him like all successful jihadist terrorists here since 9/11—if he was in the United States legally and radicalized right here on U.S. soil, rather than entering already-radicalized from abroad.  Just think: What screening process could possibly identify and exclude from the United States someone not even radicalized at his time of entry?  Surely none of President Trump’s three attempts at a travel ban would have kept him out, given that none has targeted Uzbekistan—just as none of Trump’s three attempts at a travel ban would have kept out any of the 9/11 hijackers or any of the post-9/11 successful attackers, in that all came from countries untouched by the various travel ban iterations.

Seven years ago, I wrote that “[t]he strategic success or failure of terrorist operations depends less on the terrorist thrust than on the counter-terrorist parry.”  I stand by the notion that terrorism ultimately hinges not just on what terrorists do to us but also—critically—on what they are able to get us to do to ourselves.  That makes what we see tomorrow from our leaders the beginning of our ability to assess what today really means.