To defend Winterfell against the Night King’s army of ice zombies in HBO’s Game of Thrones, Arya Stark turned to a real-world martial art: Eskrima, the official combat sport of the Philippines.

Game of Thrones star Maisie Williams, who plays the youngest (living) Stark sibling in the Emmy-winning TV adaptation of George R. R. Martin’s fantasy novels, has been put through the wringer in all eight seasons of the show. To accurately play Arya, a noble girl who travels throughout the known world to become a deadly assassin, Williams has taken up training in fencing, horseback riding, and whatever let her pull off this dope knife trick.

But for the Season 8 episode “The Long Night,” which staged the long-awaited Great Battle of Winterfell, Williams took up Filipino martial arts, or FMA. She was trained in Eskrima (also known as “Arnis” or “Kali”), a discipline characterized by the use of sticks, knives, and improvised weapons.

Of course, Williams’ Arya doesn’t exactly use Eskrima against the Night King’s undead horde. The Philippine Islands don’t exist in GRRM’s sandbox universe. But the show’s fight choreographers taught Williams an adapted version, according to Game of Thrones stunt coordinator Rowley Irlam.

“Kali is a style we drew from,” Irlam tells Inverse. “My team comes from a very wide background of martial artists and weapons experts, so we draw from all styles we possibly can. Filipino stick work is definitely one of them for this piece, as are double sword work.”

Williams’ FMA training is seen onscreen when Arya, caught in a literal tight spot, separates her new spear (forged by her friend-with-benefits, Gendry, a weapons smith) into two “sticks” that let her be more agile in close quarters.

Maisie Williams as "Arya Stark" in 'Game of Thrones' Season 8, Episode 3, "The Long Night." HBO

When it comes to stick work, especially two-handed stick work, Irlam says “there is no other discipline” to model from than FMA.

“When it comes to double stick work, [it’s] the Filipino martial art,” he says. When her spear is split into two sticks, “the nearest weapon is the Kali sticks. You draw from all styles and you try and incorporate them.”

Eskrima is an ancient martial art originating in pre-colonial Philippines. After Spain colonized in 1521, the Spanish crown feared insurrection, so it prohibited Filipinos from carrying Kampilan swords and other weapons in public. The natives adapted to using sticks and farming knives instead.

Today, eskrima thrives as the official sport of the Philippines, and is one of Hollywood’s favorite martial arts. A number of celebrity users who trained in FMA for movie roles include Denzel Washington (The Book of Eli), Melissa McCarthy (Spy), Daniel Craig (Quantum of Solace), Caity Lotz (DC’s Legends of Tomorrow), and Matt Damon (every Bourne movie).

The use of FMA in Game of Thrones came out of circumstance. During the episode’s pre-production phase, the filmmakers decided Arya would have a fight inside a tight interior stairway that was built as part of a $2 million expansion to the show’s existing Winterfell set.

Maisie Williams, training in eskrima behind the scenes of HBO's 'Game of Thrones'. HBO

Footage of a 1987 eskrima demonstration at Camp Danzan-Ryu conducted by Filipino-American martial arts expert Dan Inosanto, a renowned authority on FMA. YouTube.com/Chad Wissler

The stunts team also took advantage of Williams’ expertise in dance for her training in FMA. “Everything she learns, it’s learned in a sort of dance style,” Irlam says. “With double stick work, often the sticks are following each other. You strike with one, and the other follows through. It’s fluid.”

"If they got five hours of sleep, they were lucky.” — Rowley Irlam

Production on “The Long Night” took 11 weeks, with 55 night shoots and 70 stunt performers, says Irlam. “They would be picked up half past 12, travel the hour to the location, spend four to five hours in prosthetics, a 10-hour shoot, an hour to remove the prosthetics, and spend the hour traveling back. If they got five hours of sleep, they were lucky.”

The exhaustion had a “cumulative effect.” “The fact that all of them stayed in good spirits, remained professional, and enthusiastic, it’s a testament to the people involved. Everyone involved was very tired, on the same mission I don’t think any of us would want to revisit.”

But Irlam says the final result was worth it, especially with training Maisie Williams.

“It’s a distinct style to incorporate into her fight routine,” he says. “We were always looking for something new and original; we never wanted to repeat anything we’ve done before. None of us wanted to repeat the horse battles in the Battle of the Bastards. We wanted to make it feel grim and gruesome and scary. It needed to feel like the whole world was lost. Until Maisie’s big moment came, it needed to feel that all was lost.”

Game of Thrones airs Sundays at 9 p.m. Eastern on HBO.