On June 15, 1545, in the Lithuanian capital of Vilnius, eighteen-year-old Elizabeth of Austria, Queen of Poland and Grand Duchess of Lithuania, died of a condition that had consumed her for years. She was three weeks shy of her nineteenth birthday, and she had been queen for barely two years. The court that had once celebrated her arrival in splendour now mourned her passing in the cathedral where she was laid to rest nine days later. Her death marked the end of a marriage that had promised to seal a great political alliance and instead became one of the most tragic royal unions in early modern Europe.

Elizabeth was born on July 9, 1526, in Linz, Upper Austria, the first child of Ferdinand of Habsburg, Archduke of Austria, and his wife Anna of Bohemia and Hungary. The couple had been married for five years, and there had been growing concern that Anna might not bear children. In an era when royal marriages existed to produce heirs who could form alliances, that was a serious worry. Elizabeth’s arrival eased those fears, and her birth seemed to open the floodgates.

Anna would go on to bear fifteen children, and remarkably, most survived into adulthood. Elizabeth grew up in the Hofburg Palace in Innsbruck, surrounded by scholars, courtiers, and a devout, disciplined household. Her parents valued learning, and Elizabeth was rigorously educated in languages, the arts, and the Catholic faith. She mastered German, Italian, and French, though notably not Polish, a language that would have been far more useful in her future.

Her father’s fiery religious devotion left no room for dissent. When he discovered that one of her tutors had joked about the cardinals, he swore he would see anyone spreading Lutheran ideas executed. Around the age of four or five, Elizabeth sat for her first portrait, painted by the Austrian court painter Jakob Seisenegger. The painting shows a healthy-looking girl with red cheeks and a gentle disposition.

But all was not well. As she grew, she began to suffer from seizures, and they grew worse and more frequent over time. Modern understanding holds that Elizabeth was epileptic. In the sixteenth century, however, epilepsy was shrouded in mystery.

Some cultures treated it as a divine curse, others as communion with the divine. In Europe, the condition was barely understood, and that ignorance would cast a long shadow over Elizabeth’s life. Whispers would later claim she was being poisoned, or that the devil had touched her. The truth was simpler and more tragic.

There was no poison and no plot, only a young woman’s body betraying her as her epilepsy relentlessly worsened. The course of Elizabeth’s life was decided in the year of her birth. Less than two months after she was born, on August 29, 1526, the Battle of Mohács erupted on a plain in Hungary near the Danube. Sultan Suleiman I led a large Ottoman army into Hungary and met a considerably smaller force under King Louis II of Hungary, who was supported by lords from Transylvania and Wallachia.

The Ottomans won decisively, and Louis II was killed. He was just twenty years old and had no heir. With his death, the Jagellonian line that had ruled Hungary since 1490 came to an end, and Louis had also been king of Croatia and Bohemia. The crowns of three kingdoms now hung in the balance.

Two strong claimants emerged. One was Ferdinand, Elizabeth’s father. Through his wife Anna, sister of the dead Louis II, Ferdinand’s children carried the blood of the Jagellonian dynasty. The other claimant was John Zápolya, the Voivode of Transylvania, who enjoyed the support of the Hungarian aristocracy.

King Sigismund of Poland, whose own Jagellonian branch ruled Poland and Lithuania, did not want the Habsburgs growing stronger in central Europe. He threw his support behind Zápolya, and a brutal war of succession followed that lasted until Zápolya’s death in 1540. Ferdinand, needing to secure his claim and neutralize Polish fears, opened negotiations with the Polish court. The proposed solution was a marriage alliance built around Elizabeth.

She would marry the young King of Poland and Grand Duke of Lithuania, Sigismund II Augustus, who had been made co-ruler alongside his aging father in 1529. Marriage negotiations began in 1530. A formal treaty was signed that November, but Elizabeth was only four years old. The agreement held that the wedding would wait until she turned seven, pending papal dispensation, which was required not only for her youth but because the couple were first cousins once removed.

In time, the plan was revised, and the marriage was postponed until the early 1540s. In April 1543, at sixteen, Elizabeth finally departed Vienna for Poland. Two weeks later she arrived in Kraków, where she met for the first time the man she had been promised to for thirteen years: Sigismund II Augustus, now twenty-two. That very day, inside Wawel Cathedral, they were married, and Elizabeth was crowned Grand Duchess of Lithuania and Queen of Poland.

For the next two weeks, Kraków erupted in celebration, festivals, feasts, and fireworks. Many hoped this union would mark the dawn of lasting peace between Poland and Austria. But beneath the splendor, a darker story was beginning. Elizabeth’s health had deteriorated during the journey to Poland, and the seizures were multiplying.

Her marital situation was worse. One reason the marriage had been delayed until 1543 was the fierce opposition of Sigismund’s mother, Bona Sforza, an Italian noblewoman of the house that had ruled the Duchy of Milan. Bona was a formidable presence at the Polish court and was determined to block Habsburg expansion. She had fought the match at every turn, and once Elizabeth arrived, she made her daughter-in-law’s life miserable.

Even after the wedding, Bona continued to challenge the terms of the marriage contract and dowry. Sigismund showed little affection for his young bride and did not find her attractive. He kept several mistresses and saw them openly, even after the marriage. Far from home, Elizabeth was isolated in a foreign court, accompanied only by a small retinue of Austrians, surrounded by a hostile mother-in-law and a husband who regarded her as little more than a diplomatic pawn.

Her health continued its decline. Courtiers reported that her seizures had grown more frequent, while darker rumors spread that old Queen Bona was poisoning her. No evidence of poison was ever found, but Elizabeth’s difficult circumstances drew sympathy from many, and the Polish nobility generally admired her grace and gentleness. Their goodwill could not change her fate.

In the mid-1540s, plague swept across Eastern Europe, and the royal family fled the city for the countryside. Sigismund went to Vilnius, the capital of the Grand Duchy of Lithuania, with his favorite mistress, Barbara Radziwiłł. Elizabeth traveled through Poland with her father-in-law and mother-in-law. Sigismund I was sympathetic to her situation, but he was a feeble man in his late seventies and could do little to help.

Eventually she was reunited with her husband in Vilnius, and Sigismund attempted to make it appear that all was well in the marriage for the sake of diplomatic niceties with the Habsburgs. It was not. In Vilnius, Elizabeth’s condition deteriorated sharply. Her seizures grew ever more frequent and began to take a serious toll on her overall health.

By the early summer of 1545, it was clear she was in crisis. Her parents were written to in Austria, and their doctors hastened to her side. It was far too late. On June 15, 1545, the young queen died.

She was buried in Vilnius Cathedral nine days after her death. Sigismund II Augustus ruled Poland until his death in 1572, overseeing the formal union of Poland and the Grand Duchy of Lithuania into the Polish-Lithuanian Commonwealth. After a brief marriage to his mistress, he married Elizabeth’s younger sister, Catherine of Austria, in 1553. None of Sigismund’s three marriages produced children.

When he died, the Polish crown passed temporarily to the French royal house of Valois, and in 1575 his sister Anna ascended the throne as the last of her line, after which the House of Vasa took the crown. All the careful diplomatic scheming that had sent Elizabeth to Poland ultimately came to nothing.