We’ve had a year to reflect on and analyze Avengers: Endgame, but a mystery that continues to hang over the movie is the question of exactly how Steve Rogers traveling back into the past works. This is something that even the filmmakers can’t agree on. The Russos believe Captain America returning to the 1940s to marry Peggy Carter creates a new timeline, but writers Christopher Markus and Stephen McFeely believe Old Man Cap has simply been hanging around the MCU the whole time – like at Peggy’s funeral in Civil War – and we just didn’t know it.
The thing is, though, that if you look at the evidence, that final scene where Old Steve invites Sam Wilson to become the next Sentinel of Liberty, there’s really only one solution that makes sense. Steve must have created a new timeline because otherwise his repaired shield, which he passes on to Falcon, couldn’t exist. It’s important to note that he doesn’t take the original shield, destroyed by Thanos in the climactic battle, back with him to the past. So he had no way of fixing it.
ScreenRant suggests that what must’ve happened is that, in the separate timeline, Steve got either Howard Stark or perhaps Black Panther to create him a new vibranium shield from scratch, perhaps with the sole intention of giving it to Sam when he crossed back over to the prime timeline. We know this is a new shield as there are a few key differences between the original and Sam’s model. The silver band has a distinct line running through it and the star in the center has additional cutouts that weren’t there before.
This argument holds up, no doubt about it, though it has to be said that it’s also possible that Old Steve could’ve secretly got a new shield made at some point over the decades in the prime timeline, too. In any case, it looks like this is one more element of Avengers: Endgame that fans will be debating for a while – like whether Steve had the right ending in the first place.
