A large-scale medieval battle isn't the way you'd necessarily expect a Transformers movie to open, but a clash between King Arthur's knights and the Saxons started the action in this past summer's Transformers: The Last Knight.

With the film now available on Digital HD -- and Blu-ray in two weeks -- CBR has an exclusive first look at one of the extras from the home release, with behind-the-scenes insight into that battle sequence, including the revelation that director Michael Bay made the call to add some added horsepower, literally, to the action.

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"Originally, we were having a hundred guys on horses, and we were going to digitally put the rest in," co-producer Michael Kase said in the clip." But when it got closer to the shoot, [production designer] Jeffrey [Beecroft] was showing Michael all the overheads of Bourne Wood, where they shot Gladiator -- Michael saw the scope, and said, 'Have 200 more guys. 300 more guys.' And by the end of the day, we got 400 guys on horses."

Ian Bryce, a producer on all five Transformers films released thus far, said the scene was a complicated one to execute not just for this movie, but for the franchise in general.

"The battle sequence is one of the most complicated sequences that we undertook on the franchise, I would say, not just on this film," Bryce said in the clip. "It was really exciting, actually, and a fun part of the movie for all of us."

Starring Mark Wahlberg and Anthony Hopkins, the domestic take for Transformers: The Last Knight was the lowest in the franchise ($130.2 million), but the film was a success overseas, with international box office accounting for around 80 percent of its total gross ($604.9 million).

Transformers: The Last Knight is available on Digital HD now, and on 4K Ultra HD, Blu-ray and Blu-ray 3D on Sept. 26, along with a five-movie Blu-ray collection out that same day.