There's not a lot about the 1995 movie "Braveheart" we can call "historically accurate." William Wallace never knocked up Isabella, he wasn't all that successful as a military leader, and the movie leaves out a lot of boring (but important) trade negotiations and diplomatic meetings in Europe.
What the movie gets right, however, is that King Edward I of England really, really hated Scots.
As a matter of fact, "Longshanks" wasn't his only nickname. He also earned the moniker "Hammer of the Scots" for reasons that will be obvious to you by the end of this story, even if you haven't seen "Braveheart"
The truth is that Edward didn't necessarily hate Scotland or Scots (I think... that's never really been clear). He was just dead-set on the conquest of his neighbors. In 1274, Edward picked up where his father Henry III failed in Wales and raised an army to subdue them. After a significant uprising of people with names that are difficult to pronounce, the Welsh were put down, and Edward's son and successor was dubbed "the Prince of Wales," a practice that continues today with Prince Charles.
A decade or so later, the Scottish king, Alexander III, died suddenly and without a definite male heir. His daughter, Margaret, was just a baby when she was to be made queen, a process that was sped up to keep Edward from marrying his son to Margaret and claiming the throne by birthright. Because, believe it or not, the Scots and the English had a relatively peaceful co-existence until then.
Eventually, Edward gave the throne of Scotland to John Balliol, who was, by then, his vassal. Edward effectively controlled Scotland, using the country to bankroll his wars and provide soldiers. Eventually, the Scots became sick of this arrangement and rebelled. The Scots formed an alliance with France, England's longtime enemy, which pissed Edward off to no end. Then, William Wallace killed the sheriff of Lanark.
History doesn't record exactly why Wallace killed the Sheriff — but the execution of Wallace's wife is one possibility posited by historians. That's when the First War of Independence started.
The movie "Braveheart" depicts the murder of the sheriff as well as the 1297 Battle of Stirling Bridge. What it doesn't show is Edward I returning to Stirling in 1304 at the head of the largest collection of giant catapults ever assembled on Earth. Ever.
After cornering Scottish rebels inside the walls of Stirling Castle, Longshanks ordered the construction of 13 giant trebuchets right in view of the castle walls. It took 100 engineers months to build the massive siege weapons, the biggest of them being dubbed, "Wolf of War." The English even procured gunpowder munitions to complement the boulders being tossed at Stirling Castle. Wolf of War was so massive that it wasn't even ready for the initial barrages.
For months, the English fired at the walls of Stirling Castle, to no avail. Finally "Wolf of War" was ready in July, 1304. When the Scots saw the massive weapon and the 300-pound rocks it could hurl, they surrendered.
Having spent so much time and effort on the construction of Wolf of War, Edward rebuffed their surrender and decided to fire the massive trebuchet at them anyway. People came from far and wide for its first firing at the Scots. Edward even ordered the construction of a special siege tower with a viewing balcony so his wife could watch.
Wolf of War did what the other could not do in four months. With just a few shots, the massive weapon brought down entire sections of the castle walls. Entire buildings were smashed into rubble and only 30 Scots emerged to surrender to Edward. He had one of them drawn behind a horse and executed.