|Mishima making his speech to SDF regulars|
Noted author and actor Yukio Mishima, was plugged deeply into the elite echelons of Japanese society, was a celebrated figure in literature and film both at home and abroad, with many awards and award nominations (including nominations for the Nobel Prize in Literature), and is even today considered one of the most important figures in Japanese literature of the 20th Century.
On November 25, 1970 he entered the Ichigaya Camp of the Japanese Self Defence Forces with members of his Shield Society (楯の会 - tatenokai), took the commandant of the Eastern Command hostage, and called on members of the JSDF to rise up and overturn the government, which he considered made up of bloodless panderers who had forsaken the beautiful parts of Japanese culture and pawned them for material wealth and the illusion of consumerism.
The soldiers not only refused, they jeered him.
In the end, Mishima killed himself in a ritual suicide he had been planning for over a year - leading to speculation that he had no expectation that the coup would work, but that the whole event was a final, glorious drama. 
While Mishima was obviously driven by his own demons, he was also playing out an existential angst that continues to this day and that is rooted in that moment in Mishima's 20th year when he was told that everything he had been taught, everything that came before, was all wrong.
I think he endures because his work and his story echoes that sense of existential crisis, the continuing struggle to redefine the essence of Japan in a way that accepts what is beautiful while acknowledging the ugly parts of history, and at the same time empowers the country to take what is felt to be its rightful place on the global stage.
The struggle continues today in discussion over modification to the constitution (essentially forced on the country during the government restructuring following World War 2) to permit the JSDF to take part in peacekeeping and disaster assistance missions overseas - something they currently have very limited authority to do - and in Japan's turbulent relationship with China, Korea and some others in the region.
On the one hand, there are those who insist that the oath of pacifism enshrined in the constitution is a central tenet of the modern Japan, that confessing to and making reparations for the wrongs committed during the Imperialist era of the 20s, 30s and 40s is an obligation.
On the other hand, there are those who say that those sins have been paid for and it is time for Japan to take a place in the world more in line with its economic strength - that in fact the best way to help promote peace in the region and to make amends for the past would be to look outward and to put full strength behind development and peacekeeping projects to help their less fortunate neighbours stand beside them on the world stage.
Of course, on a third, more disturbing hand, there are those who advocate a return to the Imperial era, who want to kick out the "bad blood" of foreigners, to stand strong and proud without shame for what was done in time of war.
It's unfortunate that Mishima is today so strongly associated with the Black Van riffraff, because I think his work represents a more nuanced exploration of the issues than they seem capable of. 
He deplored what he saw as the lickspittle policies of the post-war governments, and he hated the fact that the Emperor Hirohito had disavowed his divinity - but he deplored the policies because they made Japan subject to the moral decisions of another nation rather than taking responsibility for themselves, and he hated the disavowal because he felt that having used Imperial Divinity to convince so many to die in a cause acknowledged to be wrong, the Emperor had a responsibility to take their sins on himself rather than so easily dismissing them as a lie.
Mishima was a troubled man, and he was clearly wrestling with how to reconcile the evils of the past with the need to stand strong if Japan was to enter the 21st Century as a true nation rather than one trapped in thrall to colonial powers.
He was deeply conflicted, and many of his creative works reflect that - indeed, his last work, the Sea of Fertility tetralogy, seems to use the canvas of Japan's history from 1912 to Mishima's present to paint a story of conflict and tension between the choices facing the nation. It is perhaps significant that he leaves many troubling questions unresolved in each of the four novels, even as - in some cases - the novels to some extent answer each other's questions.
Standing on the roof of the Ichigaya Camp HQ, giving his speech to the thousand or so JSDF soldiers who had gathered, he seems to have been shouting less about a true call to physical revolution, but a challenge to the whole nation:
- What are you willing to do to help Japan be reborn in its true form for the next century?
- How much are you willing to strip away to be strong?
- Are you willing to make the ultimate sacrifice and destroy what you have, your essence, as the coin to buy acceptance in the world?
Given this context, and knowing Mishima's obsession with Bushido, with the physical perfection of his body, and with youth (specifically, avoiding the decrepitude of age) it's been suggested that the whole affair may have been (at least in part) simply a way to freeze an image of himself in time, and to die as part of a grand drama.  The timing of his death, the fact he seems to have been planning the event (including his suicide) for over a year, and the echoes of his final books in his actions over that year seem to suggest it - to say nothing of the (probably apocryphal) part of the story that has him delivering the manuscript for the last novel to his editor on the morning of the events leading to his death.
Likely, this is reading far too much into things - but the key question he seems to have been struggling with in his last works remains:
Should you be willing to sacrifice the essence of what you are to achieve a rebirth that will at best be temporary, at worst an illusion?
It's a question that still haunts Japan, manifested in the current debates around constitutional reform , and is a question that some other nations find themselves faced with today.
What do you do when the essence of identity is entangled so tightly with a dark past that demands repudiation?
I would hope that Mishima's conclusion isn't the only option.
1. Born Kunitake Hiraoka
2. See also the Japan Times article marking the anniversary of this event:
3. Mishima's play "My Friend Hitler" was published two years earlier in 1968, and has often been taken along with other works and his obsession with elements of pre-war Japan such as Bushido and the Emperor as evidence he was sympathetic to uyoku dantai groups like the Nippon Dantai, There are certainly elements of fascism in his corpus and his philosophy, but ironically this particular play hints that the truth is far more complex: "My Friend Hitler" is a satirical look at the relationship between Hitler and two Nazi officials who he ultimately ordered assassinated, and has been interpreted as both preaching fascism and anti-fascism. Personally, I think this play represents the mental tension he was struggling with: a hunger for the past that was shattered when he was 20 years old (when Japan surrendered and everything he had grown up with was declared a lie) and a yearning for a future where his country could be finally absolved of its sins and be true to its roots again. His youth was a limnal time, and much of his work treads the muddy interface between opposites, so I think it's simplistic to read him as a fascist, particularly when in his own lifetime he spurned the actual fascist organizations around him and in fact he wasn't very popular among them at the time because of his stance on the culpability of Emperor Hirohito. (oddly, despite his ideas on Imperial divinity and his disapproval of Hirohito's evasion of responsibility for the actions taken in his name during and before the war, he apparently very nearly married the present Empress Michiko as a move to secure closer ties with the Imperial family. Who knows what he had in mind.)
4. Like other readers, I find myself wondering if it's possible to kill yourself ironically, and if so if that was part of Mishima's goal. Edmund Yeo's website has essay on the tetralogy by a poster named Justin that mentions this question, for example. (I suggest ignoring the apparently random cosplay photos - the essay itself is quite good)
5. Indeed, the Shield Society had its own "Committee for Constitutional Reform" that was working toward a draft for laws to enact Mishima's ideas regarding the "mistakes" that had been made in accepting the Constitution handed to the post-war government - and some of these suggestions are much the same as those being discussed today.