Shakespeare was a huge history buff, and he expected his original audiences to show up at his plays knowing a lot about English history. So, before we dive into this play, here's the quick and dirty version of events that went down before the play opens.
Long before he became England's monarch, John was one of three sons of King Henry II of England, who ruled from 1154-1189. In order of birth, Henry's sons were:
At this point in English history, the crown was traditionally passed down from a father to his eldest son. When Henry II died, his eldest son, Richard was crowned King Richard I (a.k.a. "Richard the Lionheart," or "Richard Coeur-de-lion," if you use the fancy French term like Shakespeare does).
Of course, you don't earn a title like Richard the Lionheart by staying at home and sitting on your duff. Shortly after becoming king, Richard went off on a crusade to the Middle East. While he was gone, he left England in the hands of a committee of noblemen.
One nobleman who wasn't part of this committee was John, Richard's youngest brother. As you can imagine, John wasn't too pleased with this, and in no time he was scheming to take power away from the committee of noblemen. Does any of this sound familiar? That's right: this is the period of history featured in movies about Robin Hood, where the evil "Prince John" is usually the main bad guy. (Most historians think that the Robin Hood story is probably a myth, though.)
Anyhow, a big piece of luck came John's way in 1192, when he learned that Richard had been captured on his way back from the Third Crusade by the Duke of Austria. While John and Richard's mother, Eleanor of Aquitaine, raised money for Richard's ransom, John teamed up with King Philip to try to prevent Richard from being released.
But this didn't work. By 1194, Richard was out of prison and back in England. Believe it or not, he actually forgave John for plotting against him.
When Richard was dying in 1199, he announced that he was leaving his kingdom to his little brother, John. So John finally hit the jackpot, right? Well, yes, but there was only one problem: haven't we been forgetting somebody in this whole story? What about Geoffrey, the middle son of old King Henry II? Why didn't he become king after Richard's death? He was older than John, after all, right?
Geoffrey couldn't become king after Richard died because, well, he himself was dead—and had been for 13 years. However, before he died, Geoffrey had a son: Arthur, the Duke of Brittany. Because Geoffrey was older than John, and thus next in line for the crown, some people (especially in Shakespeare's day) argued that the crown should have gone straight to Geoffrey's son, Arthur—not to John.
And now we're ready to see how it all went down after that.