I never had much time for the Empress Elizabeth. She was just 16 when she married the Habsburg emperor Franz Joseph, in Vienna in 1854, and from the very first she seemed to me willful, self-obsessed, and unready for the role she had taken on. Within days of her marriage, “Sisi,” as she was known for short, was skipping official functions.

Long holidays followed, sans husband—he had a vast, sprawling empire to manage. Although known as the Habsburg or Austrian Empire, it reached much farther than modern-day Austria, stretching from the Swiss Alps to Transylvania, in what is now Romania, and from today’s Poland to Bosnia, in the Balkans. Lacking imagination but convinced of his own abilities, Franz Joseph was not up to the job of running it.

Where was his wife? Once she had done her duty by siring an heir, in 1858, she was traveling on yachts in the Mediterranean, playing cards at the casinos of Monte Carlo, riding to hounds in England and Ireland, and hiking in Hungary. Elizabeth was preoccupied by her appearance and figure, taking three hours over her hair each morning, exercising vigorously (her gymnastic equipment is still on show in Vienna’s Hofburg Palace), and sleeping in a mask of raw meat in the hope of ridding her skin of wrinkles. For most of her life, she kept her waist at 16.5 inches, pinched in by tight corsets.

Upon Further Reflection …

I had seen several of the empress’s artistic commissions—the cutesy murals in her hunting lodge on the outskirts of Vienna, and, in Corfu, the kitsch interiors of the royal Achilleion Palace. But it was only when I chanced upon a volume of her poetry in a Vienna bookshop that my estimation of her changed. Her verse is good—mournful, haunting, and reflective. It is written in the style of the German Romantic poet Heinrich Heine, but is neither derivative nor wooden. Above all else, it conveys a sad loneliness.

Emperor Franz Joseph and Empress Elizabeth. Correspondence between the two evokes a couple in love.

Following her life with renewed interest, I read the correspondence between Franz Joseph and Elizabeth. (His letters to her survive, but not hers to him.) His letters are warm and affectionate. They share family news and private jokes—Franz Joseph’s close companion, the burly opera singer Frau Schratt, for instance, is either “the girlfriend” or, on account of her tantrums, the “minister of war.” The emperor signs off “your little one” or “the manikin.” (He was shorter than she.)

Once she had done her duty by siring an heir, in 1858, the empress was traveling on yachts in the Mediterranean. But her poetry revealed itself as mournful, haunting, and reflective.

Surprisingly, several of the letters are in cipher. These tell an even deeper story, for all are concerned with Hungarian politics. Franz Joseph’s reign lasted almost 70 years. The first decades were consumed by the problem of Hungary. Although the kingdom of Hungary had been a part of the Habsburg Empire since the 16th century, Hungarians were not reconciled to rule from Vienna. As recently as 1848–49, they had fought a war of independence. It had failed, and Franz Joseph had extracted a brutal revenge. But the Hungarians refused to be broken—their political leaders scorned the emperor for the harshness of his rule and plotted with his enemy, the Prussians.

The empress liked Hungary and the Hungarians. She valued the lack of stiff ceremony in the court there, which reminded her of her Bavarian upbringing in the ducal castle at Possenhofen. She welcomed, too, the gallant attentions of the Hungarian aristocrats and, in particular, of the glamorous Count Gyula Andrássy. Andrássy was also the one who introduced Elizabeth to the lawyer and politician Ferenc Deák, who could see a way out of the constitutional impasse—a method of giving Hungary independence within the Habsburg Empire.

The empress was not responsible for the deal that Franz Joseph struck with the Hungarians, for he would have had to come to terms with them eventually, and the details and constitutional arguments were Deák’s. But she pressed him to at least start discussions, made the introductions, and spurred him on. The letters in code are his updates to her on the negotiations, written almost as if to elicit her approval.

Italian anarchist Luigi Lucheni, arrested in Geneva following his murder of the empress.

The bargain was eventually struck in 1867. Hungary would have almost complete home rule, but it would recognize Franz Joseph as king, thereby staying within the framework of the Habsburg Empire. This meant that the Austrian Empire would have to be refashioned as the Austro-Hungarian Empire, with two capitals—one in Vienna and the other in Pest-Buda (later renamed Budapest). In June 1867, the emperor was crowned king of Hungary, but on this occasion the Hungarian Holy Crown was briefly placed on Elizabeth’s head, too. It was an honor never before given to a Hungarian queen and a public acknowledgment of the role she had played in reconciling Hungary to its Habsburg ruler.

The letters in code are Franz Joseph’s updates to Elizabeth on the negotiations, written almost as if to elicit her approval.

The next decades were sad ones for the empress. She flitted between spas and palaces, traveling incognito and evading crowds for fear that her aged face would appear in the newspapers. The suicide of her son, Rudolf, in 1889, sent her into a bleak depression. Eleven years later, she was murdered on the shore of Lake Geneva by an anarchist looking for anyone royal to pull a gun on.

Elizabeth was buried in the Capuchin Crypt, in Vienna, which is where most Habsburgs have ended up. Her tomb was originally to bear the simple inscription “Elizabeth, Empress of Austria,” but at Hungarian insistence the title “Queen of Hungary” was added. It was a suitable epitaph that acknowledges her role in the making of the Austro-Hungarian Empire and the importance of those letters written in code.

Martyn Rady is a professor of Central European history at University College London and the author of The Habsburgs: To Rule the World, published by Basic Books