The question here may be less will they and more have they. CIA Director John Brennan told CBS’ 60 Minutes that he views ISIS attempts to attack the US as “inevitable.” He follows that up by saying that successful attacks are not necessarily inevitable, but have they already taken place?

Scott Pelley: Is ISIS coming here? John Brennan: I think ISIL does want to eventually find it’s, it’s mark here. Scott Pelley: You’re expecting an attack in the United States? John Brennan: I’m expecting them to try to put in place the operatives, the material or whatever else that they need to do or to incite people to carry out these attacks, clearly. So I believe that their attempts are inevitable. I don’t think their successes necessarily are.

What constitutes an attack attempt? The San Bernardino attack at least appears to qualify. At least one of the two perpetrators, Tashfeen Malik, came to the US after becoming radicalized abroad and may have posted pro-ISIS propaganda online during the attack. Syed Farook reportedly had conducted “overseas communications” with people the FBI suspected of organizing terrorism. Two weeks before the attack, Farook got $28,500 under mysterious circumstances.

For a larger-scale attack, ISIS might face more difficulties; at least they haven’t attempted a Paris-style attack here yet. Brennan tells CBS that the Paris attacks were a failure of intelligence, and a lesson to his own organization:

Scott Pelley: What did you learn from Paris? John Brennan: That there is a lot that ISIL probably has underway that we don’t have obviously full insight into. We knew the system was blinking red. We knew just in the days before that ISIL was trying to carry out something. But the individuals involved have been able to take advantage of the newly available means of communication that are–that are walled off, from law enforcement officials. … We gotta work harder. We have to work harder. We need to have the capabilities, the technical capabilities, the human sources. We need to be able to have advanced notice about this so that we can take this– the steps to stop them. Believe me, intelligence security services have stopped numerous attacks– operatives– that have been moved from maybe the Iraq to Syria theater into Europe. They have been stopped and interdicted and arrested and detained and debriefed because of very, very good intelligence.

And that’s doubly important, now that ISIS has increased its capabilities in a very alarming direction:

Scott Pelley: Does ISIS have chemical weapons? John Brennan: We have a number of instances where ISIL has used chemical munitions on the battlefield. Scott Pelley: Artillery shells. John Brennan: Sure. Yeah. Scott Pelley: ISIS has access to chemical artillery shells? John Brennan: Uh-huh (affirm). There are reports that ISIS has access to chemical precursors and munitions that they can use.

Interestingly, Reuters corroborated that claim in an exclusive report this afternoon:

Islamic State militants attacked Kurdish forces in Iraq with mustard gas last year, in the first known use of chemical weapons in Iraq since the fall of Saddam Hussein, a diplomat said, after tests by the global chemical arms watchdog. A source at the Organization for the Prohibition of Chemical Weapons (OPCW) confirmed that laboratory tests had come back positive for the sulfur mustard, after around 35 Kurdish troops were sickened on the battlefield last August. The OPCW will not identify who used the chemical agent. But the diplomat, speaking on condition of anonymity because the findings have not yet been released, said the result confirmed that chemical weapons had been used by Islamic State fighters.

All of the above underscores the need for a forward strategy against ISIS rather than a reactive strategy. The US and its allies have tried to pick apart ISIS with a light precision-bombing campaign, but the terror quasi-state has expanded into Libya and moved to weapons of mass destruction in the meantime. Brennan says the CIA is doing its part, with both intelligence and operational covert assets on the ground. That would help destroy ISIS as part of a massive, coordinated offensive to dislodge, isolate, and trap ISIS’ army, but the air-alone war appears to have only done mild damage and encouraged ISIS to harden its assets. Brennan has a tough job, but an even tougher task selling current US strategy against ISIS as anywhere close to sufficient for the administration’s declared goals.

Watch the entire interview below: