We see the Survey Corps gearing up for combat, and then walking off into the light, possibly to glory, or possibly to their deaths.
This is followed by the famous arm behind the back, fist over the heart salute that nerds around the world sometimes perform in solidarity for our love of the series.
We then see them leaping off the wall into a horde of titans, with the chorus singing, “Sasageyo. Sasageyo,” as the song’s title, “Shinzou wo Sadageyo” roughly translates to “Dedicate your hearts.”
Attack on Titan Season 3 - Official Opening | OP1 [ RED SWAN ]