When Iranian-backed militias attacked the U.S. embassy in Baghdad, Ayatollah Khamanei reportedly boasted that America “cannot do a damn thing” about it. This harked back to America’s failed effort in 1979 to rescue hostages Iran held. During a demonstration in Tehran following that fiasco, one of the signs said, “America can’t do anything.”

All nations respect nations that can do things — in other words, nations that effectively wield power. They tend to view nations that can’t with contempt.

Iran, I think, is particularly impressed by the effective wielding of power. At the beginning of World War II, the then-Shah (father of the one we remember) incurred the displeasure of the British, who thought he was too sympathetic to Germany. The British responded by forcing this powerful dictator to abdicate in favor of his son (the Shah we remember). The old Shah was sent into exile and died during the war.

In the early 1950s, the new Shah appointed the popular Mohammad Mosaddegh as prime minister. Mosaddegh proceeded to nationalize the oil industry, to the chagrin of the British. The British persuaded President Eisenhower to help them oust Mosaddegh. The Shah, who had left for Rome, returned to take back the reins.

These exercises of power made a lasting impression on Iranians. So lasting, that for decades, and long after the sun had set on the British empire, Iranians of a certain age attributed to the British everything important that happened in the Middle East.

As late as the 1990s, my law firm was involved in litigation between very high level Iranian ex-pats. The partner in charge of the litigation told me how puzzled he was that, for some reason, the old Iranians he dealt with saw the hand of Britain everywhere.

A new generation of Iranians formed a very different impression when it came to America. The humiliation the mullahs inflicted on us in 1979 caused them to believe, as that sign said, America can’t do anything.

The overthrow of Saddam Hussein temporarily changed this impression. So much so that, according to our intelligence services, Iran halted its nuclear program. It had seen how America responded to evidence that a hostile power in the region was developing weapons of mass destruction. We could do something big in the region, after all.

Unfortunately, the U.S soon met with serious reversals in Iraq. Thus, Iran’s nuclear program soon was back in business (assuming it really had been halted).

Then came the Obama administration. Suddenly, it wasn’t just that America couldn’t do anything to stop Iran. Now, it no longer even wanted to. On the contrary, Obama was prepared to subsidize the regime — to pay it tribute. We had become truly pathetic in the eyes of Iran’s tough-minded rulers.

President Trump quickly reversed course. And now, by effectuating the killing of Gen. Soleimani, he has demonstrated, in a way he hadn’t previously, that the U.S. can some do some impressive military things to Iran, and is willing to do them.

I’d like to say that, with this demonstrated, Iran will back off. Unfortunately, that seems unlikely.

For one thing, the regime needs to save face. For another, it holds some good cards. It controls strong militias throughout the region and, I assume, terrorist cells in key parts of the world including, perhaps, America.

The U.S., by contrast, seems to be spread pretty thin in the region. And President Trump clearly doesn’t want a massive redeployment of troops to Iraq, much less a ground war with Iran and its militias.

Thus, I expect Iran to deploy some of its military assets to hit back at the U.S.

However, the U.S. holds the best card. We can take the fight to Iran in ways it cannot take the fight to us.

My sense, then, is that President Trump will have to keep demonstrating what the U.S. can do to Iran. If he does, Iran probably will finally get the message and stop short of forcing Trump to crush the regime. If he doesn’t, Iran will regain its confidence and continue to be a menace.

Trump, though, seems determined not to let that happen.