It is a montage of clips from the most expensive film ever made (in today's dollars the budget would be over $700 million). The movie is Sergei Bondarchuk's War & Peace, made in Russia in the mid-60's, and these scenes are from the Battle of Borodino, an hour long battle sequence. These were the days before CG animation, there are no special effects creating these huge armies, it is all REAL. 120,000 soldiers in period costumes, thousands of horses, etc. No film will ever come close to this in terms of spectacle, without being, essentially, a work of animation (like The Return of the King).