American history is full of presidents making promises they cannot keep. At the Republican National Convention in 1988, George H.W. Bush famously said, “Read my lips: no new taxes.” Two years later, he signed a budget deal that raised taxes in order to reduce the deficit. President Obama, for his part, promised Americans that, under Obamacare, they always could keep their health plans if they liked them. That proved untrue—and he was forced to announce an administrative fix to quell the ensuing political firestorm.

This past week, Obama has made another promise that he may not be able to keep. “I want the American people to understand how this effort will be different from the wars in Iraq and Afghanistan,” the president said last week when he announced the new strategy to degrade the Islamic State. “It will not involve American combat troops fighting on foreign soil.” While those two sentences may assuage the public, they are disingenuous. We don’t know how these military engagements will unfold. If we’ve learned anything from Iraq and Afghanistan, it is that the Middle East is unpredictable and we must be prepared for everything.

On Tuesday at a hearing before the Senate Armed Services Committee, General Martin Dempsey, the chairman of the Joint Chiefs of Staff, demonstrated just how quickly “no boots on the ground” can change. “My view at this point is that this coalition is the appropriate way forward. I believe that will prove true,” he said. “But if it fails to be true, and if there are threats to the United States, then I, of course, would go back to the president and make a recommendation that may include the use of U.S. military ground forces.” These comments provoked an immediate backlash as they seemed to contradict the White House’s position. The Pentagon and White House both attempted to walk back those comments later, but neither actually refuted what Dempsey said.

This is emblematic of the inherent contradiction in Obama’s strategy. He can promise no troops on the ground, but cannot be certain of it. That’s effectively what General Dempsey is saying—and he’s correct. For the same reason, Obama’s commitment to “degrade and ultimately destroy” the Islamic State makes little sense if he rules out putting boots on the ground. Robert Gates, Obama’s first defense secretary, said as much Wednesday when he said, “There will be boots on the ground if there's to be any hope of success in the strategy.”

That doesn’t mean that Obama’s plan is wrong. Airstrikes may be the correct strategy with the goal of destroying IS likely unattainable. (In fact, I think airstrikes in Syria are the correct move, although I’m less sure about arming the so-called moderate rebels.) But whatever the merits of Obama's plan, he should be more candid where it could lead. That doesn’t mean admitting failure before the mission even begins, obviously. But he could have said,While we can never know for sure what the future will hold, I can assure you that I have no plan of putting American troops on the ground. I have no intention of letting this become another Afghanistan or Iraq." That may have diminished support for his strategy, but it’s support he shouldn’t have had in the first place, because Obama is getting it under false pretense. He simply cannot promise there will be no ground troops—and if he does, the American people shouldn’t believe it.

While the president glosses over the potential consequences of this military engagement, Congress is notably absent as well. Neither party wants to vote on the authorization to use military force in Syria for political reasons. The White House says it would welcome approval by Congress, but has the legal authority to conduct airstrikes without Congressional action under the 2001 Authorization for Use of Military Force (AUMF) and 2002 AUMF. As my colleague Jessica Schulberg has written, that authority is dubious at best.

This legal rationale also sets a dangerous precedent. If the administration has the authority to conduct airstrikes in Syria and Iraq without further action from Congress, then it could also put troops on the ground without approval from the legislative branch. Obama may not worry about this possibility—either because he is committed to consulting with Congress if U.S. troops become necessary or because he has fooled himself into believing that there is not situation where troops will be necessary. But what about the next administration? This military engagement is almost certain to extend past 2016. If President Ted Cruz wants to escalate military action in Iraq and Syria, he could use the Obama administration’s legal reasoning and bypass Congress. If nothing else, that should scare the president into consulting with Congress.

Washington pundits have written many columns critiquing the president for a lack of leadership and Congress for a lack of action over the past few years. Sometimes those criticisms were warranted. Other times they weren’t. But the abdication of leadership right now is striking. We're about to embark on a multi-year military engagement under dubious legal authority with Congress abdicating its legislative duty and a president unwilling to level with the American people about the potential for future escalation. That’s a scary situation.