The Hobbit: The Battle of the Five Armies' will conclude with a 45-minute battle sequence.
The news has been confirmed by acclaimed director Peter Jackson, who's assured fans of the trilogy that measures are being put in place to ensure they do not suffer ''battle fatigue''.
Speaking to Entertainment Weekly, the 52 year old explained: ''We have a rule that we're not allowed more than two or three shots of anonymous people fighting without cutting back to our principal characters.
''Otherwise the audience just ends up with battle fatigue.''
The New Zealander explained that a great deal of preparatory work went into the spectacular battle scenes, which take place at the bottom of the Lonely Mountain.
Jackson - who also directed 'The Lord of the Rings' trilogy - said: ''We had to design the landscape itself and figure out, 'OK, if we have 10,000 orcs, how much room are they going to take up?'
'''Are they going to fill up the valley or look like a speck?' Then we could start drawing the arrows on the schematics.''
He said, too, that eagles will play a role in the battle scenes, but not in the way fans have come to expect.
Jackson remarked: ''[author J.R.R.] Tolkien uses eagles in a way that can be kind of awkward because they tend to show up out of the blue and change things pretty quickly.
''So here they're just part of the plan, not the saviours. I mean, I do realise that if the eagles had just been able to bring Frodo to Mount Doom in 'Lord of the Rings' and let him drop the ring in, those movies would have been much shorter.''
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