If you’re the only son and heir of the King of England, maybe it’s best to be extra careful when traveling. Sadly, William Adelin, son of Henry I of England, chose to set sail at night in the White Ship, which struck a hidden rock and quickly capsized and sank, taking all but one of the passengers with it on November 25, 1120. The loss of William would kick off a succession crisis that would result in a bloody and prolonged civil war.
William Adelin had one living sibling: Matilda (sometimes called Maude), whose husband was Henry V, Holy Roman Emperor. Henry I had his barons swear to support her as his heir, but they were dubious, since no woman had ever ruled England, and women are such frail things, they couldn’t possibly handle it, could they? After Henry died in 1135, his nephew, Stephen, usurped the throne, snatching out from underneath Matilda as well as his two older brothers. Matilda and her second husband, Geoffrey of Anjou, declared war on Stephen, and things got very messy very quickly.
The period of civil war, known as The Anarchy, lasted until 1154 and made the whole country miserable. It finally e3nded with the Treaty of Wallingford, in which Stephen agreed to recognize Matilda’s son, Henry, as his heir in return for remaining on the throne. Stephen died in 1154 and Henry, along with his wife, Eleanor of Aquitaine, was crowned at Westminster Abbey, ushering in the Plantagenet Dynasty.