It’s hardly surprising that the new secretary of defense, Ash Carter, emerged from a long meeting in Kuwait with American generals and diplomats to pronounce himself satisfied with the campaign against the Islamic State (ISIS). Imagine the headlines if the new Pentagon chief had said that the campaign was unsatisfactory! But what counts is not what Carter says for public consumption. The real question is whether he has swallowed the Kool-Aid or not–and whether his generals have too.

It’s not easy to tell from his public comments, which amount to saying that the Islamic State is “hardly invincible” and that its “lasting defeat … can and will be accomplished.” That may be true, but he left unclear exactly how and when its defeat will be accomplished.

Certainly in the case of Syria–where the U.S. has all but given up training the Free Syrian Army–it is hard to see any ground force on the horizon capable of beating ISIS unless it belongs to Hezbollah, whose victory would hardly be much of an improvement. In Iraq, there is slightly more reason for hope but only if the U.S. relies on Iranian-backed Shiite militias whose takeover, again, would not be any improvement on ISIS.

Lately senior U.S. officers have been bragging that Mosul will be liberated as soon as April or May. But it seems unlikely that this feat could be accomplished by majority Sunni forces since little progress has been made in mobilizing Sunni tribes and the Iraqi Security Forces, which were designed to be genuinely multi-sectarian, have largely fallen apart. That leaves the Shiite militias and the Kurdish peshmerga as the most capable striking forces, but neither one has any credibility in west Mosul, the Sunni part of town.

It’s possible that the assault force could penetrate Mosul and win some victories against the relatively small number of Islamic State militants who are said to be garrisoning the town–especially if the White House lifts the prohibition on allowing U.S. Special Operations Forces and combat-air-controllers to accompany the assault force into battle. But it’s hard to imagine how they could possibly hold the city afterwards. Unless the U.S. can cobble together a capable and credible Sunni force, the likely result would be long-term chaos, with continuing urban warfare that would allow the Islamic State and/or other extremist groups to assert their influence once again.

And that’s to focus only on the difficulty of driving ISIS out of Mosul. Don’t forget that ISIS also controls much of the rest of the Sunni Triangle in Iraq. And no matter how hard-pressed ISIS becomes in Iraq, it can always simply cross the Iraq-Syria border and regroup within its Syrian territory where, as previously mentioned, it remains virtually unchallenged.

Ash Carter is a smart guy. Presumably he knows all this. The question, impossible to answer from the outside, is whether he still genuinely believes ISIS is on its way to defeat or whether he’s just making such statements for public consumption. Whichever the case, he has embarked on a dangerous start to his tenure in office, because happy talk for public consumption has a way of overriding any private concerns and taking control of the official mindset. We have already seen the high cost of having an overly optimistic secretary of defense who buys bogus claims of progress from his generals. We can’t afford to repeat the mistakes of Iraq in 2003-2007.