(RNS) — Many Christian leaders, including Pope Leo XIV, have expressed deep concern about the war in Iran and called for diplomacy. Although some are pacifists, most Christians recognize that sometimes war is necessary and just, as philosophers and theologians for centuries have discussed and debated the criteria for a just war and its application in their times.

Most, for example, believe that World War II, fought against the Axis powers, was a just war. Others, like the wars in Iraq and Afghanistan, are hotly debated. 

Is the current fight against Iran a just war?

The traditional criteria for a just war include that it is a just cause, it uses just means, it has a probability of success and it is initiated by legitimate authority.

Wars of defense have been the easiest to defend, which is why the Allied response to attacks by Germany and Japan is considered a just war. Likewise, Ukraine’s response to the Russian invasion is clearly a defensive war and justifiable. The first Persian Gulf War that repelled Iraq from Kuwait could also be described as a defensive war. Similarly, the Korean War.

Is an offensive war ever justified? Traditionally, the answer has been yes, but popes, including John Paul II, have practically closed that loophole. John Paul opposed the wars in Iraq and Afghanistan. On the other hand, he supported what he called “humanitarian intervention” in Bosnia to stop genocide. This would be considered a just cause.

Another argument for starting a war is that it is necessary to stop an imminent threat to the nation.

When I was a child in the 1950s, some military theorists even argued for a preemptive nuclear strike against the Soviet Union to protect us from attack. Luckily, wiser heads prevailed. But the United States has since gotten involved in many more limited wars to stop first the spread of communism, and later the spread of terrorism.

Too often, however, the excuses for war are based on lies or false intelligence. For example, Russian President Vladimir Putin has lied to his people to justify his war with Ukraine.

The U.S. Congress approved the Gulf of Tonkin Resolution for Vietnam in 1964, based on lies or false intelligence, which became the legal basis for entering the Vietnam War. More than 50 years later, the victory of the Vietnamese communists has not proved to be as disastrous for the U.S. as predicted. While the Vietnamese people are not free, the country is now closer to us than to China. Lives and money were wasted in a war that never should have been fought.

Likewise, the 2003 invasion of Iraq was premised on the existence of weapons of mass destruction that did not actually exist. True, Saddam Hussein is gone and Iraq has a fledgling democracy, but at what cost? Hundreds of thousands were killed. The invasion led to the rise of the Islamic State group. The country is severely divided with Iran-supported militias. No one knows what would have happened if we had stayed out of the war.

With this record, it is not unreasonable to question what governments say to defend their wars.

President Donald Trump has said the Iranians were close to developing nuclear weapons, even though only a few months ago he said he had destroyed Iran’s nuclear potential. He has presented no evidence that Iran is an imminent threat to the U.S. This sounds too much like the threat of weapons of mass destruction that got us into war with Iraq. And Trump’s record of lying does not inspire confidence.

He also says he is helping the Iranians overthrow their government, although U.S. efforts at regime change have rarely been successful. If he does achieve regime change, he will accomplish what previous presidents wanted but failed to do. But it is more likely that calling Iranians to attack their government will lead to the deaths of tens of thousands of protesters and no change.

This is not to say that Trump’s war has accomplished nothing. It has assassinated Ayatollah Ali Khamenei, a ruthless dictator who was responsible for the deaths of thousands of Iranians, Iraqis, Americans and Israelis through supplying militias and terrorists with arms and money. I shed no tears that he and his top lieutenants are gone.

However, have we created a martyr who would have been dead soon anyway from natural causes? Will the deep state he created outlast the current attack? Prior to the attack, he had instructed top Iranian leaders to create lines of succession three stages deep so it would be clear who was in charge no matter how many people were killed. Such a state could still repress its people and wage asymmetric warfare and terrorism around the world.

On the other hand, what could be the most successful outcome of the war is the destruction of Iran as a military threat to Israel and Arab countries in the region. This was made easier by excellent intelligence and by the fact that Israel had already severely degraded Iranian allies such as Hezbollah and Hamas.

In the initial attack, anti-aircraft defenses were taken out so that the U.S. and Israel would have absolute air superiority. Next came the missiles and drones capable of hitting Israel and its neighbors. Finally, Iran’s navy, which can threaten oil shipments in the gulf.

But destroying Iran’s stockpile of missiles and drones will not be sufficient. Also needing to be destroyed are the factories that build them. The destruction of drone factories will also help Ukraine since Iran is a major supplier of drones to Russia. This will take weeks. Israel understands this better than Trump, who originally said he wanted a short war of a few days.

And if Iran is to be kept in check, it will require periodic incursions to take out any Iranian attempts to rebuild its antiaircraft, nuclear, missile and drone capacity. This conflict could go on for years and could be very costly even if it only involves airpower.

The alternative is to walk away and have another major war in 10 years after Iran rebuilds. But such an ongoing war could deplete U.S. supplies of weaponry that are needed in Ukraine and elsewhere, for example, to deter China’s ambitions against Taiwan. 

Meanwhile, we have to protect oil shipments in the Persian Gulf and keep open the Strait of Hormuz, through which 20% of the world’s oil and liquid natural gas flows. This is not easy when a mine or a small boat packed with explosives can take out a tanker. If we do not allow Iran to sell its oil, it will want to disrupt the world’s oil supply, and pressure will be put on the U.S. and Israel to end the war. The higher prices for oil and gas from a protracted conflict would be bad news for consumers but good news for fossil fuel producers in the U.S., especially since the Trump administration has opposed expansion of green energy.

Even if a war has a good cause, it must also have a good chance of success if it is to be considered a just war. As has been shown, the chances of Trump’s war against Iran succeeding are low. Regime change is unlikely. And although Iranian missiles and drones can be taken out from the air, keeping them from being replaced could take years of continued conflict. And destroying Iran’s ability to wage asymmetric warfare is almost impossible.

Finally, a just war must be initiated by a legitimate authority. In the U.S., that would be Congress, which did not approve the war. Internationally, that should also involve the United Nations. Trump is acting like an absolute monarch who can wage war whenever and wherever he pleases.

You do not need to be a pacifist to question Trump’s war against Iran. It has serious shortcomings when examined through the lens of the just war theory.