This week, President Obama will become the first sitting U.S. president to visit Hiroshima, the Japanese city that the United States nearly destroyed with a nuclear bomb in 1945. While the bombing is estimated to have killed as many as 150,000 people, Obama is not expected to apologize during his visit.

It's reasonable to ask, after more than 70 years, why not apologize for Hiroshima? One well-worn argument is that the bombing of the city (and the atomic bombing of Nagasaki that followed) was morally justifiable as it was the quickest way to end World War II — a conflict that had already taken millions of lives.

But another argument is broader and perhaps even more persuasive: Apologizing simply isn't something the United States does, nor do many other countries. "We don't apologize, ever," said Jennifer Lind, a professor at Dartmouth College and the author of Sorry States: Apologies in International Politics.

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The Hiroshima Genbaku Dome after the bombing — Photo: Shigeo Hayashi

This isn't a unique facet of American diplomacy, either. "Countries in general do not apologize for violence against other countries," Lind added, noting that Germany and, to a lesser degree, Japan are outliers, as they have actually apologized.

But what else has America not apologized for? Here are a few ideas.

Agent Orange in Vietnam

During the Vietnam War, the United States sprayed about 12 million gallons of Agent Orange, a herbicide, over areas of Vietnam, Cambodia and Laos in a bid to both remove cover for Vietcong and North Vietnamese fighters and kill food crops. Since then, the Red Cross of Vietnam has estimated that about 1 million people were disabled or suffered health problems because of contact with the herbicide.

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U.S. Army helicopter spraying Agent Orange over Vietnamese agricultural land — Photo: Huey Defoliation National Archives

While the United States has sometimes disputed the link between Agent Orange and health problems, it has contributed more than $100 million to help clean up the herbicide aftermath. Congress has also allocated (far smaller) sums to health and disability programs that often target those who may have been harmed by Agent Orange. However, there has been no apology for this or for other controversies of the war, such as widespread U.S. use of landmines.

The 1953 coup in Iran

In 1953, democratically elected Iranian Prime Minister Mohammed Mossadegh was overthrown in a coup. In Mossadegh's place, Mohammad Reza Pahlavi was reinstalled as the shah of Iran, overseeing policies that were widely seen as restrictive and corrupt. The shah was in turn ousted from office by the 1979 Iranian revolution, which installed Iran's current Islamic theocracy.

In declassified documents, the CIA has acknowledged that the overthrow of Mossadegh was "carried out under CIA direction as an act of U.S. foreign policy, conceived and approved at the highest levels of government," with the aid of the British Secret Intelligence Service.

However, the United States and Britain have never apologized for their role in the coup, with the Obama administration recently stating that it had no plans to. The negative effects of the coup have been acknowledged by some U.S. figures, notably former secretary of state Madeleine Albright. "The coup was clearly a setback for Iran's political development," Albright said in 2000. "And it is easy to see now why many Iranians continue to resent this intervention by America in their internal affairs."

The United States is also widely suspected of involvement in a bloody 1973 coup that ousted socialist Chilean President Salvador Allende in 1973 and put dictator Augusto Pinochet in control of the country. Pinochet would go on to lead the country for 17 years, during which his regime was accused of the rampant use of abduction, torture and murder. The CIA has denied any direct involvement in the coup, though it acknowledged it had been opposed to Allende's presidency.

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Salvador Allende in the early 1970s — Photo: Biblioteca del Congreso Nacional - Chile

In 1977, Brady Tyson, deputy leader of the U.S. delegation to the U.N. Human Rights Commission in Geneva, did attempt to offer an apology for the U.S. involvement in the coup, but he was quickly disavowed by the State Department. When Obama traveled to Chile in 2011, he brushed aside a request for an apology from a Chilean reporter. "The history of relations between the United States and Latin America have at times been extremely rocky and have at times been difficult," Obama said. "But we're not trapped by our history."

The West African slave trade

The U.S. Congress offered an apology for slavery to African Americans in 2009 (though it was specifically worded in a way that meant it could not be used as a legal rationale for reparations). But what apologies have been made to the African countries whose modern history the slave trade helped shape?

Not a lot, it turns out. Bill Clinton came close to making an apology during a presidential trip to Uganda in 1998. "Going back to the time before we were even a nation, European Americans received the fruits of the slave trade," Clinton had told a crowd in a village outside Kampala, the Ugandan capital, in what were said to be impromptu remarks. "And we were wrong in that."

At the time, critics quickly argued that the wording of the comments implied regret rather than a formal apology. And the location was odd: Most slaves came from West Africa, not Uganda. Clinton had been in Senegal just a week before, where the comments may have carried far more weight.

Patrice Lumumba was the first democratically elected prime minister of Congo. However, he was ousted just 12 weeks into his term and then killed four months after that on July 2, 1961. The assassination, which took place just seven months after his country's independence from Belgium and in the heat of the Cold War, has come to be viewed as a disaster for the troubled country.

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Mobutu and Nixon in 1973 — Photo: Jack E. Kightlinger/Wikimedia Commons

Belgium would acknowledge its role in the assassination in 2002 and offer its official apologies for the move. It's unclear whether the CIA had any direct link to that plot, but it is known that it carried out huge covert operations in Congo during this period. The United States would soon go on to support dictator Joseph-Desiré Mobutu (who later changed his name to Mobutu Sese Seko) and his immensely corrupt regime for decades. No apologies have been made.

The U.S.-led invasion of Iraq in 2003 is clearly one of the most controversial moments in recent history. Even if the war took out dictator Saddam Hussein, many would argue that it brought chaos to the wider region that persists to this day. At the least, the death toll among Iraqis was huge, though estimates are depressingly vague: Most suggest that a few hundred thousand people lost their lives, at the least.

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The April 2003 toppling of Saddam Hussein's statue in Baghdad — Photo: U.S. DoD

George W. Bush, the U.S. president who ordered that invasion, has expressed some remorse for the faulty intelligence touted in the run-up to the conflict, but he has refused requests to apologize for the invasion itself. "I'm convinced that if Hussein were in power today, the world would be much worse off," he told CNN expand=1] in 2010, denying that the war had been a "lost cause."

On July 3, 1988, the USS Vincennes fired two surface-to-air missiles at an aircraft it mistakenly believed was an Iranian F-14 fighter flying over the Persian Gulf. Instead, the plane was actually Iran Air Flight 655 — a civilian airliner flying from the nearby Bandar Abbas International Airport, bound for Dubai. All 290 passengers and crew on board were killed.

The shoot-down happened at a time of tension between Iran and the United States, which was at that point backing Iraq in its war with Tehran. Despite the tragic nature of the incident, Washington offered little contrition. George H.W. Bush, the U.S. vice president at the time who was then on the campaign trail for the upcoming election, was even quoted as saying, "I will never apologize for the United States — I don't care what the facts are" (though this was not in direct reference to Iran Air Flight 655).

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An Iranian stamp commemorating the Iran Air Flight 655 incident — Photo: Wikimedia Commons

In 1996, President Bill Clinton expressed regret over the incident, and the United States paid the Iranian government $131.8 million in compensation, with around $61.8 million going to the families of those killed. But no formal apology or acknowledgment of wrongdoing was ever made.

Looking over this short list (and thinking of the numerous other events out there that we missed), it might be reasonable to wonder when America has actually apologized for foreign events. There are a few pretty clear examples: The United States apologized in 2010 for American experiments on Guatemalans in the 1940s, for example, and in 1993, it said sorry for its role in the 1893 overthrow of the Hawaiian monarchy. Also, Washington does tend to apologize more readily for smaller-scale incidents: In 2012, Obama apologized profusely for U.S. military involvement in the burning of copies of the Koran in Afghanistan in 2012.

But overall, apologies tend to be the exception and non-apologies the rule. The logic here is not moral but rather political. Apologies are often controversial from the apologizers' side, Lind explained, which means that the apology may be tempered or halfhearted. In turn, people in the country receiving the apology are often not satisfied, creating more political headaches. There are further discussions about what actually constitutes an official apology and how it could affect calls for legal reparations.