Breaking up, as Lord Byron wrote in “When We Two Parted,” is devastating: “If I should meet thee/ After long years, / How should I greet thee?— / With silence and tears.” But there is something uniquely tragic about lovers separated by cruel circumstance. Their stories reappear in literature as a warning about fate, a celebration of idealism or a lament for lost love.

One of the oldest examples to come down to us is the thwarted union between the Roman emperor Titus (A.D. 40-81) and Berenice, princess of Judea and queen of Chalcis (A.D. 28-sometime after 81). Like Romeo and Juliet, their relationship was doomed from the outset. Berenice risked her life trying to preserve the peace between Romans and Jews in the period leading up to the First Jewish-Roman War, A.D. 66-73. Titus was the Roman general whose army was besieging Jerusalem. Nevertheless, the two fell passionately in love.

Their relationship survived Titus’ destruction of the Second Temple in 70 and the subsequent Roman slaughter of almost a million Jews. But when he inherited the throne in 79, Rome balked at the idea of a Jewish empress. Forced to choose between love and duty, Titus reluctantly chose duty, establishing a tradition of royal self-sacrifice that would continue untilEdward VIII abdicated in order to marry Wallis Simpson. Titus died—killed, possibly—two years into his reign. Berenice disappeared around the same time, her fate unknown.

In Paris 1,100 years later, a teacher and his pupil embarked on a secret love affair, leaving behind a literary legacy that still resonates today. Peter Abelard (1079-1142) was a celebrated philosopher and theologian, Héloïse d’Argenteuil (circa 1100-1164) a brilliant young scholar whose renown brought her to Abelard’s attention.

After Héloïse gave birth to a son, the couple married secretly to avoid scandal. But the marriage became public and Héloïse’s furious family took their revenge: Hired henchmen broke into Abelard’s bedroom and castrated him. The two lovers became a monk and a nun. But the relationship continued, albeit in a different form, through their letters.

Abelard became resigned to his fate, but Héloïse remained a lifelong rebel. Prefiguring Second Wave feminism by 900 years, she would become an inspiration to her modern sisters by her denunciation of traditional marriage: “What woman will be able to bear the constant filth and squalor of babies?”

In the 19th century, the House of Habsburg suffered a catastrophic loss when the bodies of Crown Prince Rudolf of Austria and his teenage mistress, Baroness Mary Vetsera, were found on Jan. 30, 1889, at his hunting lodge near Mayerling. Rudolf’s father, it was rumored, had ordered his son to break off the affair, and Rudolf had chosen death instead of duty. Others claimed that Mary had died during a botched abortion and Rudolf had killed himself in remorse.

The mystery of what really happened at Mayerling only ended this summer with the release of Mary’s letters, recently discovered in the Austrian National Library. They reveal that the lovers had indeed made a suicide pact. “Dear Mother / Please forgive me for what I’ve done / I could not resist love…I am happier in death than life,” the 17-year-old wrote. Rudolf and Mary’s act deprived the Austro-Hungarian Empire of an heir. The line of succession moved to Rudolf’s cousin, Franz Ferdinand, whose assassination in 1914 started World War I.

Again, it is Lord Byron who best describes the impact of star-crossed lovers on historical consciousness: “As stars that shoot along the sky / Shine brightest as they fall from high.”