system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can a battle go on for weeks?

Whenever I'm reading about a battle, they often lasted for weeks or even months. How does that work? I assume it's not just one long, weeks-long round of movement, firing, flanking, etc., but what does a weeks-long battle actually look like?
gpt
You have your guys dug in along the front, and the other guy has their guys dug in along a different front.  Movements push the line around, but holding recently taken ground is hard.  The lines might be different every day but it takes a long time to gain a decisive advantage or wipe out the other guy.

You see a lot less of this in modern (post Korea) times, both sides use more mobility and try to avoid direct assaults where they don't have a significant numerical advantage.