In August 1910, in a date that to Americans might seem like ancient history but in northeast Asia is remembered as if it were yesterday, the Empire of Japan formally annexed what had once been the sovereign nation of Korea. It is only now, over a century later, that Japan and Korea have formally reconciled one of the darkest legacies of that era: the 1930s and '40s recruitment of Korean women and girls as sex slaves known as "comfort women."

Japan's imperialism in Korea ended in 1945, and Japan re-normalized relations with South Korea in 1965, but the psychological wounds it inflicted there have never fully healed. Japan and South Korea have, ever since, been locked in a sort of unspoken negotiation over this past; over how to remember this chapter in their shared history — a question that is still unresolved within Japan itself.

In recent years, that conversation has focused overwhelmingly on one issue: "comfort women." During Japan's imperial wars in Asia, it forced thousands of girls and women to become sex slaves for Japanese troops. It called these girls and women, many of whom were Korean, "comfort women."

On Monday, Japan and South Korea have reached an official agreement that they say will close their years-long dispute over Japan's guilt and responsibility for enslaving Koreans as "comfort women." The terms of the agreement are still forthcoming, but it appears that Japan will officially admit wrongdoing and offer an $8 million compensation fund for victims, and in return South Korea will promise to stop raising the issue.

But this is about much more than just the comfort women issue. It's about litigating what kind of country Japan is allowed to be, both in the history books and in the world today. It's about shaping the 21st century order in Asia. And the story of why this is happening at all — and why only now, nearly a century later — goes back to some grave and long-lasting American mistakes in its wartime occupation of Japan.

What are "comfort women"?

A Korean survivor of wartime Japanese sexual slavery weeps at a conference of survivors (KAZUHIRO NOGI/AFP/Getty)

In 1931, Imperial Japan invaded Manchuria, launching what many Asians consider the start of World War II. As the Japanese Imperial Army pushed into China and then Southeast Asia, it began establishing "comfort stations" in its military bases and along the front lines.

The "comfort stations" were named for their official purpose: to comfort the brave Japanese soldiers fighting for the empire abroad. They are sometimes described as like brothels, but that's not what they were. In fact, they were camps in which the Japanese military imprisoned non-Japanese women and girls, whom Japanese soldiers would routinely rape, often dozens of times per day.

Japan first recruited "comfort women" largely from Korean communities, both in Japan and in Korea itself. It used Korean police to recruit the women and girls, and would often lure them with false promises of a good job in the city. The women were then shipped to military bases, often near the front lines in China, where they were locked up in rooms only three-by-five feet, and raped by as many as 60 to 70 soldiers every day.

"She was then taken to the courtyard and in front of all of us, her head was cut off with a sword and her body was cut into small pieces"

Throughout the War, as the Japanese army spread across Asia, it forcibly seized tens (or possibly hundreds) of thousands of women and girls from the countries it invaded. In Korea, it dropped its charade of peacefully recruiting women, and began overtly raiding villages, at times killing family members who tried to stop them. According to a 1996 United Nations report, the raids often targeted schools and many of the victims were children aged 14 to 18 — so that the military cold ensure their virginity.

The horror of these comfort stations is difficult to overstate. The UN report includes, for example, these representative accounts from two survivors, both Korean. (Thanks to NPR's Elise Hu for flagging these).

"We had to serve over 5,000 Japanese soldiers as sex slaves every day — up to 40 men per day. Each time I protested, they hit me or stuffed rags in my mouth. One held a matchstick to my private parts until I obeyed him. One Korean girl caught a venereal disease from being raped so often and, as a result, over 50 Japanese soldiers were infected. In order to stop the disease from spreading and to ’sterilize’ the Korean girl, they stuck a hot iron bar in her private parts." — Testimony of Chong Ok Sun

"One day, a new girl was put in the compartment next to me. She tried to resist the men and bit one of them in his arm. She was then taken to the courtyard and in front of all of us, her head was cut off with a sword and her body was cut into small pieces." — Testimony of Hwang So Gyun

The comfort stations were about more than just providing Japanese soldiers with sex. The Imperial Japanese Army was steeped in fascist militarism and a twisted obsession with racial hierarchies, which led it to systematize many abuses, including the mass rape of "inferior" women and girls in the foreign lands it conquered.

Some historical accounts say the comfort stations were meant as a release valve; by institutionalizing rape on military bases, Japan could better control its soldiers and prevent mass rapes outside the base. Other accounts suggest it was a deliberate effort to inculcate soldiers with the idea that rape was an acceptable and in fact desirable tool of war. In either case, the point is that this was part of Japan's larger practices of using war crimes such as mass rapes and mass murders of civilians.

These abuses are remembered especially in Korea, though not all comfort women were Korean. And that gets to the ways that this is about much more than even Japan's sexual enslavement practices, as horrific as they were, and is also about the things that came after.

The "comfort women" controversy isn't just about the war — it's about what happened after the war

Emperor Hirohito, who was never prosecuted for his role in Japanese wartime abuses under his reign, with US President Jimmy Carter in 1979 (Kurita KAKU/Gamma-Rapho via Getty)

Japan's abuses during World War II extended far beyond sexual slavery, and it's only in recent years that "comfort women" have become an enormous political issue in Asia. And that speaks to the ways in which this is about more than just Japan's imperial past. It's also very much about the present.

In South Korea, talking about "comfort women" is, in some senses, a way of expressing the commonly held view that Japan's crimes against Korea have never fully been reconciled; that the Korean survivors have never really had justice and so remain victims. And that this is a kind of metaphor for Korea's continuing national victimhood.

Koreans are not wrong to feel this way, and it goes back to the very first days after Japan's defeat in 1945 — and America's failures in how it handled Japan's defeat.

In both Germany and Japan, the allies held war crimes tribunals, meant to punish those responsible but also to force an historical accounting, so that the victims might feel they'd received justice. But, in Japan, the war crimes tribunal was dominated by Western powers, and focused overwhelmingly on Japanese crimes against Western people and interests. Only three of the 11 judges were Asian, though most of Japan's victims had been Asian, and none of those three were Korean.

"The trial was fundamentally a white man's tribunal," the historian John Dower wrote. "It was especially perverse that no Korean served as judge or prosecutor. ... [Japan's Asian victims] were not allowed to judge their former overlords or to participate in preparing the case agains them. The plight of the Koreans was, in its way, emblematic of the larger anomaly of victor's justice as practiced in Tokyo."

America's decision to keep Hirohito in power "had a lasting and profoundly distorting impact on Japanese understanding of the lost war"

Germany's victims in Europe had been allowed to participate in the war crimes investigation. They came away with a sense that justice had been done and their grievances addressed, which made it easier for them to learn to coexist peacefully with the Germans who had done such awful things. Koreans (and, for that matter, Chinese) never had this experience, and it has fed a sense of injustice ever since.

There was another important difference between Japan and Germany: the German Nazi-era system was completely abolished and Nazis themselves banned. Germans were forced, if slowly, to acknowledge their wartime crimes and admit their wrongdoing. Adolf Hitler became a reviled figure even in Germany itself.

But, in Japan, the Americans declined to do any of this. The American military planned to occupy Japan for years. It feared that abolishing the Japanese government entirely, as they'd done in Germany, would provoke a popular backlash that could become a violent uprising. Or it could open a vacuum that might be filled with communists. The Americans thus refused to depose Japan's wartime leader, Emperor Hirohito, who remained in power (with less authority, but on the throne) until 1989. The Americans turned these old imperial institutions into puppets for their own rule.

It wasn't just Hirohito who escaped full justice. It was, in some ways, the Japanese people themselves. Both the American occupiers and the imperial remnants allowed or even encouraged a polite fiction that Japanese abuses in Asia hadn't been so bad, or had been limited to a few bad apples. As the historian Herbert Bix wrote, the American efforts to preserve Hirohito and brush his crimes under the rug "had a lasting and profoundly distorting impact on Japanese understanding of the lost war."

This is why, 70 years later, Germans widely agree that Nazism was a terrible mistake, that German crimes were just as bad as the victims contend, and that the entire German nation was complicit. Meanwhile, in Japan, that hasn't really happened, at least to the same extent.

Senior Japanese leaders routinely visit a quasi-religious shrine that honors fascist-era war criminals. Japanese politicians openly debate whether the wartime abuses were really so bad — with some arguing that "comfort women" were not slaves but rather happy volunteers. Japanese nationalism is becoming popular again, and with that has come more revisionism of Japan's war crimes.

All of this has robbed Koreans and Chinese and many other Asian nations of a sense that justice was ever really done. It's part of why 75-year-old Japanese war crimes don't feel like they happened 75 years ago, but rather are a continuing insult and injustice that persists, a wound that has never been allowed to heal and is re-opened every time a Japanese politician expresses admiration for imperial leaders or downplays imperial abuses. To them, it's not in the past at all.

How "comfort women" became such a big issue, and why it's happening now

Korean survivors of Japanese wartime sexual slavery at a 1995 rally for justice near the Japanese embassy (CHOO YOUN-KONG/AFP/Getty)

Why, of all of Japan's wartime crimes, is it this one that has become such a major controversy? Why only now, 70 years after the war ended?

This is, in some ways, a Korean story. While Americans today associate South Korea with risqué K-pop music videos, the country was for a very long time deeply, deeply socially conservative (and remains more socially conservative than may be immediately obvious to Westerners). Korean girls and women came home to find their own families and communities blamed them for their rapes. Isolated and often estranged, they were pressured into silence.

It wasn't until 1991, when a Korean "comfort woman" survivor spoke out, that others came forward as well. They weren't just confronting Japan, but their own societies that had forced this issue into the dark. Since then, more have spoken out — and Koreans, now more socially liberal, have listened.

In 1993, only two years later, the Japanese government formally apologized with the Kono statement, acknowledging its guilt and the government's wrongdoing. But the 1993 apology immediately become a political controversy in Japan — with Japanese conservatives condemning it, disputing Japanese guilt, and making sure that this Korean wound stayed open.

Since then, within Japanese politics, debating the Kono statement has been a way of debating Japan's own wartime history. It is, in some ways, an argument that is more about Japan today: How guilty should we feel about our past? Should that shame dictate how we act toward our neighbors? Is it really right that once-great Japan should be so submissive and apologetic?

These debates aren't really about 1940s wartime abuses, but rather about whether Japan today gets to be a proud and powerful country, or whether it has to be the kind of country that apologizes to its former colonial subjects and suffers the humiliation of America's continued military presence. But these debates have often played out, within Japanese politics, on the question of "comfort women" and whether Japan was right to apologize.

Japanese conservative leaders, many of whom are nationalists who want Japan to rebuild its military and once again become a proud Asian power, thus tend to downplay the comfort women issue. This started becoming a much bigger issue in 2012, when Japanese conservatives took back control of the government, now led by conservative Prime Minister Shinzo Abe.

Abe had for years argued that the comfort women claims were overblown; in 2007, during his (very brief) first tenure as prime minister, he passed a cabinet resolution claiming that there was no official proof the women had been coerced at all. On returning to power in 2012, Abe has issued a lot more nationalist rhetoric and has been frequently accused of whitewashing imperial-era crimes or even glorifying them. He's also rolled back restrictions on Japan's military that had been imposed as part of Japan's 1945 surrender, and has tried to remake Japan as a regional power once more.

So Abe's government has been hesitant to admit guilt for wartime abuses, partly because this would anger nationalist Japanese voters who are tired of being told to apologize, and partly because it would cut against Abe's desire to roll back Japanese pacifism. But this has just dragged out the issue, infuriating Japan's neighbors, isolating the country within Asia, and emboldening a Japanese far-right that actively celebrates their fascist past.

There's another important dimension to all this: there is still a substantial Korean minority in Japan. And those Koreans still endure discrimination and racism today. It's very different from, say, Jews in Germany who can expect not just equal treatment but robust legal protections and social norms that forbid anti-Semitism. And it contributes to a sense among Koreans, fairly or unfairly, that Japan is unrepentant and perhaps, in some ways, unchanged.

What's in the Japan-South Korea agreement and why it's a big deal

South Korean President Park Geun-hye and Japanese Prime Minister Shinzo Abe in 2014 (SAUL LOEB/AFP/Getty)

The agreement that Japan and South Korea reached on Monday goes much further than the 1993 apology. Japan will offer $8 million in compensation to the remaining Korean survivors (who number only a few dozen) and will officially apologize. Abe will also make clear he's apologizing in his official capacity as prime minister, something that was left vague in 1993.

In return, South Korea will promise not to raise the issue again, which is another way of saying that they will consider it officially resolved.

But in many ways it's not about what they agreed to, but rather how they agreed to it, that matters here.

Japan's 1993 apology was done unilaterally, whereas this agreement was reached by bilateral consensus between the two countries. Jennifer Lind, a Dartmouth professor who studies northeast Asian politics, pointed out that this means there is "buy-in" from South Korea, thus giving Koreans a voice in the agreement and a sense that they were not just apologized to but heard themselves.

Lind also emphasized that this agreement was made by a conservative Japanese government — "the very faction that has been so critical of [Japanese] liberal leaders offering apologies and so forth." That's a big deal for getting not just the Japanese government but the Japanese people to accept the apology as legitimate.

"So this time, the group that would be the most likely to denounce such an agreement is the one that negotiated it," Lind told me. "This bodes well that it will be accepted in Japanese society."

In other words, this agreement brings together the two factions that were left unsatisfied by the 1993 agreement: Japanese conservatives, who disavowed it, and South Koreans, who'd felt left out.

Why Japan is finally apologizing now, and what it means for Asia

Japanese Prime Minister Shinzo Abe (KAZUHIRO NOGI/AFP/Getty)

If you watch or read American media, you will probably come away with the impression that this is happening because the United States government pressured its two allies into making up, and that this is all about the US trying to build strong Asian alliances so as to counter China. But those issues are really secondary here. This is in fact primarily about Japan and South Korea and what they want, not the US or China.

"The big decision today was Seoul’s," Lind said. "This agreement reflects that Seoul is more willing to deal with Tokyo than it had been before, when it was freezing Tokyo out completely."

South Korea's leaders, in other words, decided they were ready to resolve the issue. Lind says this in part because South Korean and Japanese interests happened to be lining up more fully anyway.

"You need to reverse the causal arrow," Lind said when I asked if this agreement would improve Korea-Japan relations. "It’s not the agreement that causes relations to get better. It’s the leaders’ desire to make relations better that caused the agreement."

The US, she pointed out, has been trying to bring South Korea and Japan together since the 1950s, and has never really been able to push either country toward the other.

To some degree, Abe may be feeling like he needed to do this. Not to please the Americans or to counter the Chinese, not primarily at least, but rather to give himself more room to continue growing Japan's military and rolling back Japanese pacifism (the country has been officially "pacifist" since the end of World War II).

Since taking office, Abe has slowly re-militarized Japan, which he seems to earnestly consider both necessary and part of his legacy. But those policies have been unpopular among Japanese voters. Perhaps Abe initially thought that stirring up nationalism (for example by downplaying Japan's enslavement of comfort women) would generate popularity for his militarism policies. But that didn't really work, and it worsened relations with South Korea and China, which just ended up making his militarization policies even more controversial. So, regardless of what Abe really believes about comfort women, he may have concluded that apologizing for them would grant him more space to continue growing Japan's military, which is likely what he cares about more.