Warning: Major spoilers below if you have not seen "Avengers: Endgame."

The "Avengers: Endgame" editors Jeffrey Ford and Matthew Schmidt look back on the more than yearlong process of editing "Avengers: Infinity War" and "Endgame" back-to-back.

The two movies combined had 900 hours of footage shot.

Huge changes were made on "Endgame" in postproduction, including Black Widow's major scene in the movie and how the Battle of New York in "The Avengers" was introduced in the time-travel portion of the movie.

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Warning: Major spoilers below if you have not seen "Avengers: Endgame."

Jeffrey Ford and Matthew Schmidt talk with pride about their work on "Avengers: Endgame" and "Avengers: Infinity War." It would be hard not to. For the past two years, the editors have done little else but work on crafting not one but two Marvel movies, each of which is now among the biggest box-office earners of all time.

But in talking to Ford and Schmidt, there are times when you can hear in their voices just how difficult it was. Their tone changes from upbeat to serious, and their descriptions fill with words like "slog," "pressure," and "intense."

Starting in January 2017, the two were part of the core creative team that crafted the conclusion of the Marvel Cinematic Universe's Infinity Saga with the making of "Infinity War" and "Endgame." The duo edited the two movies back-to-back, which often meant they were cutting at the same time the directors Anthony and Joe Russo were still shooting the movie.

"We were cutting every day, we were refining, we were figuring out what we were going to reshoot, figuring out what we had to finish," Ford told Business Insider. "It was a constant state of preproduction, production, and postproduction all at the same time for almost a year straight."

The editors Jeffrey Ford and Matthew Schmidt edited "Infinity War" and Endgame" back-to-back. Marvel "And then when we finished that year of insanity," Ford continued, "we went right into an absolutely hellish, almost impossible postproduction period that lasted from January to April when we delivered 'Infinity War,' and that was one of the most intense periods of filmmaking I ever experienced, and I have worked on some crazy movies."

Before working on "Infinity War" and "Endgame," Ford's credits included MCU titles like "Captain America: The First Avenger," "The Avengers," and "Avengers: Age of Ultron." Throughout most of it, Schmidt has been by his side, first as an assistant editor starting with the first "Avengers" movie and then sharing editing credit with Ford beginning on "Captain America: The Winter Soldier."

And having an editing duo is almost essential for how MCU titles are churned out. While Ford was wrapping post on "Infinity War," Schmidt continued assembling the "Endgame" footage while the Russos were shooting so they would not have to wait on seeing edited sequences.

Read more: Director of dark indies, lover of American accents, and fan of psychology essays: Karen Gillan is much more than Nebula from the Marvel Cinematic Universe

"We showed them a version of 'Endgame' [within] about a week, week and a half of principal photography being done," Schmidt said.

In total, Ford said over 900 hours of material was shot between the two movies.

"It was a massive amount of footage with three, sometimes four units working every day pumping out material," Ford said. "And I'm not even including the motion-capture footage. But if you do a bit at a time, you can get through it."

Within the epic journey to edit the movies came some decisions that changed how scenes and sequences were put together at the script stage. That's especially true of "Endgame," which along with the typical MCU blueprint of big battles and dramatic moments also had the added element of featuring footage from previous MCU movies for its time-travel plot — leading to major tweaks.

Below, Ford and Schmidt explain how "Endgame" evolved in the edit suite: