Juana the Mad, Queen of Castile and Aragon, was famously locked up by the men in her life for—as they claimed—being insane. Juana was the daughter of Queen Isabella I and King Fernando II, who ruled over most of the Iberian peninsula. With her horrid husband Philip the Fair, who was the son of the Holy Roman Emperor, Juana had six children, including four daughters. All four became queens-consort in great nations across the continent. The second-youngest, Mary, was married to the King of Hungary, whom she dearly loved, until his tragic end in battle. Remaining a widow for the rest of her life, she was a dutiful sister to her brothers, reluctantly serving as both regent of Hungary and Governor of the Netherlands on their requests. She was a true Habsburg.

Juana’s third daughter and fifth child, Mary, was born in Brussels on the 15th of September, 1505. Mary grew up in her aunt Margaret’s care, in the Netherlands, following her mother’s incarceration, along with her siblings Eleanor, Charles, and Isabella. Her other siblings, Ferdinand and Catherine, were brought up in Spain. She was given a phenomenal education by her aunt, learning many languages and developing a love for music as an avid player of the clavichord. Mary had inherited the infamous Habsburg jaw and due to such features, she was not considered very attractive.

At the tender age of six months, Mary was betrothed to the child of the King of Hungary, Louis, who was unborn at the time. Mary’s elder brother, Ferdinand, would be married to Louis’s elder sister, forging a double alliance between Hungary and the Habsburgs. And when Mary was ten years old, she was married off to nine-year-old Louis. Louis had been crowned king of Hungary and then king of Bohemia while his father was still alive so that there would be no questions over succession. This was a smart choice, as Louis’s father died shortly after Louis and Mary’s wedding, leaving them as King and Queen of Hungary.

The ascension of a child was followed by much fighting among the nobility of Hungary, which left the kingdom bankrupt and disordered. In all this, Louis was left as a neglected pawn. His government refused to pay their annual tribute to the Ottomans and sent the severed head of the Ottoman ambassador back to Sultan Suleiman. Such decisions had been taken as Hungary had expected aid from other European nations. However, as funds were squandered by the nobility, Hungary’s defenses grew weaker, and the unrest grew to a point where Mary was forced to flee Hungary for Innsbruck.

In Innsbruck, she was well-taken care of by her paternal grandfather, Maximilian, Holy Roman Emperor, who taught her the art of warfare and hunting, and she grew incredibly close to him. When he died in 1519, she decided she could no longer remain in Innsbruck, and made the treacherous journey back to Buda despite being warned against it. Mary’s assistance served to strengthen Louis’s rule. It was written of her, “If only she could be changed into a king, our affairs would be in better shape.” Her coronation as Queen took place in 1521, and she soon began to take over many aspects of the rule of Hungary.

Martin Luther himself was an acquaintance of Queen Mary, who dedicated four psalms to her. Both she and her sister Isabella were fascinated by his ideas but distanced themselves from him due to pressure from their brother, Ferdinand. She grew to be a patron of the arts, collecting many works including the famous Arnolfini Portrait, by Jan van Eyck, which she obtained later in life. Meanwhile, Hungary’s state was the opposite of improved, and sensing this weakness, the Ottomans declared war. They made significant advances into Hungarian territory, and the Austrian aid Louis was receiving did nothing to better the situation. Louis himself was killed at the Battle of Mohacs, which ended in an Ottoman victory and would leave Hungary divided between the Ottomans, the Habsburgs, and the principality of Transylvania.

Mary and Louis had died childless, and so Ferdinand, using his position as the husband of Louis’s sister, attempted to claim the Hungarian throne and gathered some support. He was elected as king in Bohemia and declared Mary as his regent in Hungary (a post which she had initially declined). Ferdinand denied her request to resign as regent, though she was allowed to step down once Ferdinand arrived in Hungary.

Then, John Zapolya, the son of the former Palatine of Hungary, won the crown temporarily and asked to marry Mary. Ferdinand later succeeded in claiming the throne of Hungary and offered Mary the regency once more. She declined, refused to remarry for the rest of her life, and left Hungary for Vienna. Once Margaret of Austria, her aunt who had raised her, died, both Mary’s brothers pestered her to take Margaret’s position as Governor of the Netherlands.

She agreed, and along with governorship, she received guardianship of her two nieces, Dorothea and Christina, Isabella’s two daughters. Francesco II Sforza, Duke of Milan, proposed marriage to 11-year-old Christina. Mary’s brother, Charles, the Holy Roman Emperor, was ecstatic and allowed the marriage to go ahead. He also allowed for the 38-year-old duke to immediately consummate his marriage to the child Christina. Mary argued for Christina, saying she was far too young for consummation, which Charles ignored. Mary managed to delay the wedding and Christina’s departure to Milan, though only by a few months. This would not be the first issue over which Charles and Mary disagreed.

As governor, Mary was allowed to make decisions in most departments excluding military affairs and was many times forced to go along with Charles’s decisions regarding the Netherlands, though she could not disagree more. She and Charles often argued over such matters, and he had once written to her, “You are a woman. You are not allowed to speak of such things.” Mary had a far more tolerant approach to the Reformation but was forced to repress Protestantism in the Netherlands on her brother’s orders, a task which she carried out as minimally as she could.

Mary requested many times to resign from the governorship of the Netherlands, a position which had drained her mentally and physically. When Charles abdicated the emperorship, Mary expressed her desire to resign once more, and this time she was allowed to step down. She left for Spain, where Charles and Eleanor soon joined her. Both died in quick succession, with Eleanor dying in Mary’s arms in February 1558. Charles, who was growing ill, requested that Mary return to the governorship of the Netherlands, and she finally agreed. Mary had seen her leadership of the Netherlands as a failure due to her perception that she was powerless as a woman, yet she was determined to return to fulfill her brother’s wish following Charles’s death in September 1558. Mary herself would die less than a month later, in October 1558, following two grief-stricken heart attacks. She had lived to the grand age of 53 years old and never got the chance to return to the Netherlands.