Let id Software clue you in about what DOOM’s “push forward combat” means.
Bethesda has released another video talking about DOOM’s combat and how the enemy speed force you to always be on the move. The segment is cut from Bethesda’s E3 2015 developer Q&A. Towards the end, the developers reveal that later in the game you’ll be looking to kill small enemies for health drops, if you can’t find them in the world.
Which is the literal meaning of killing to stay alive.
It’s also where the quote “Bruce Lee with a shotgun on a skateboard” originated, which you either love or hate.