By tradition, today is the date of the completion of the printing of the Gutenberg Bible, which is probably one of the most influential texts of European history.
You can read all over the place about how the use of movable type changed the way that literature and scholarship was done for hundreds of years, so I won’t just add another voice to an already overcrowded field. Instead, how about I answer the question: What else was going on in 1455?
In England, in only a few months, the Wars of the Roses would begin in earnest. By May 22, with the First Battle of St Albans, the state of England would begin a process that would steep it in blood for the next thirty years.
Across the sea, in the Americas, the Aztecs had just completed an expansion to the Great Temple, which was completed with a fire ceremony atop the new building. This ceremony marked a shift in the calendar, beginning a new cycle, and may have been overseen by Moctezuma I.
In Africa, Luiz de Cadamosto, who had been hired by Henry the Navigator, prince of Portugal, began his explorations of the River Gambia. This, combined with the papal encyclical released earlier that year allowing for non-Christians to be taken as slaves, is recognized as one of the key moments in the development of the slave trade.
Elsewhere, in Korea, Sejo of Joseon forced his nephew to abdicate and declared himself king. Whereas his nephew had been largely impotent and unable to rule (shades of Henry VI), Sejo managed to steer the ship of state with a remarkable certainty over his 13 year reign.
So yeah, there’s something a little more than the usual “on this day” for you. Think of anything I missed? let me know.