"Initially we based Battle of the Bastards on the Battle of Agincourt which took place between the French and English in 1415," explained director Miguel Sapochnik in an interview with Entertainment Weekly. "But as needs changed, as did budgets, it became more like the Battle of Cannae between the Romans and Hannibal in 216 BC."
How did they film this thing?
Very carefully! Any battle scene is a logistical and scheduling nightmare for a production staff, but judging from interviews with Sapochnik, this was a particularly challenging shoot. Thanks to three days of constant rain, the production had to make some last-minute changes from the original script that D.B. Weiss and David Benioff provided. Like Jon Snow, the crew had the odds stacked against them.
"Finding a way to cram in and organize everything so that we would use every single minute well in order to squeeze every ounce we could out of our time was the most logistically complicated thing I've ever been involved in," Sapochnik told EW. "When all was said and done, we had around 500 extras, 160 tons of gravel, 70 horses and riders, 65 stuntmen and women, seven principle actors, often four camera crews, 25 days to shoot it, and a call sheet with often up to 600 crew members."