Pigs?

Making the movie even more ridiculous than it already was.

In the Middle Ages a classic tactic to capture a castle was to have your sappers dig a tunnel up to the castle and create a hollow space under the walls, supported by timbers like in a mine. Then they would lay a fire under those timber supports with plenty of combustibles such as oil, and leg it out of the mine fast before it took hold. The timber supports would burn and the walls would collapse into the hollow beneath them, leaving a breach in the walls through which the besieging army could enter.

This was done in the siege of Rochester: the mine was dug under one of the corner towers of the castle. The king ordered forty fat pigs to be collected and slaughtered, and their fat rendered down. This pork fat was used to ensure that the fire burned fiercely. It worked just as planned and the tower fell down. (It was rebuilt later in the latest style, which is why today Rochester Castle has three square towers and one round one.)

But, idiotically, the director decided to show live pigs being pushed into the tunnel and burned, even though he certainly knew this wasn't how they had been used IRL, and furthermore that pigs (like people) being more than 60% water, you cannot fuel a fire with pig meat. Actually the exact opposite; you need a whole load of fuel to cook, let alone burn, a pig.