The United States has joined Israel in opening a war with Iran. For the last half century, Iran has fomented destabilizing terror in the Middle East while violently suppressing voices of opposition by its own people. The world would be a safer place without the theocratic regime of Iran.

But is that the goal?

It is hard to know the mission because President Trump and his closest advisors have presented shifting narratives, sometimes in the same day, on why the United States is fighting. Regime change? A free Iran? Destruction of nuclear facilities? Elimination of Iran’s ballistic missile threat? Unconditional surrender? Support for Israel, Iran’s sworn enemy? Retaliation for what the administration said was an imminent attack? All of the above?

Trump said in the Oval Office this week, “We won this” and Iran is offering “a very significant prize,” though he did not elaborate. Iran said its demands for peace included lifting all sanctions, closing all U.S. bases in the Gulf, financial reparations, and keeping its missile program.

These are two very different versions. The military talks of the “fog of war.” This is the “fog of peace.”

It is reasonable and appropriate for Americans to ask these questions when their country goes to war. American lives and treasure are at stake. General Dwight Eisenhower, in his order encouraging soldiers before the D-Day invasion, wrote, “In company with our brave Allies and brothers-in-arms on other Fronts, you will bring about the destruction of the German war machine, the elimination of Nazi tyranny over oppressed peoples of Europe, and security for ourselves in a free world.”

America knew what it was fighting for.

Without a specific and targeted justification for the Iran war, Americans will quickly become impatient. That impatience grows each time we pull into the gas station and see that the prices have surged again. That experience, which happens an estimated 30 million times a day, prompts the question, “What am I paying for?”

A Reuters/Ipsos poll found that Trump’s approval rating has fallen to its lowest level–36 percent–since he returned to the White House. “Only 29 percent of the country approves of Trump’s economic stewardship.” A CBS poll found that 57 percent said the war is going “very or somewhat badly.”

That is problematic for Trump since in stark military terms, the U.S. and Israel have achieved overwhelming success with the airstrikes. U.S. Central Command reports over 10,000 targets have been struck and more than 140 Iranian vessels damaged or destroyed. That is military dominance. However, Iran’s ability to close the Strait of Hormuz represents a strategic advantage.

Retired Gen. Stanley McChrystal, who was in charge of Joint Special Operations Command from 2003 to 2008, told the New York Times, “It is like what we found in Iraq. We could bomb Iraq pretty easily; we could even take Baghdad with relative ease. We could get rid of the existing government. But once we wanted to change the reality on the ground, who actually controlled things, how things worked, now you’re not at 30,000 feet. You’re at six feet.”

And that is the conundrum for Trump, as it is with every leader who has tried–usually unsuccessfully–to control the situation from the air. Inserting ground forces means casualties, which will be human tragedies and make the war even less popular at home.

But that brings us back to the fundamental question: What is the United States trying to achieve? The often-studied Prussian military tactician Carl von Clausewitz said, “No one starts a war–or rather, no one in his sense ought to do so–without first being clear in his mind what he intends to achieve by war and how he intends to conduct it.”

As an American, I always want us to win every skirmish, every battle, every war in which we are engaged. I sincerely hope that our military will prevail in this fight with minimal loss to our side. But Americans are entitled to a clearer message from our president on what exactly we are fighting for and what will constitute victory.