War..Check Consequences...Check No Romance....Check I think someone needs to tell anime producers that romance is more difficult to write than action. Just have two dudes in a room punch each other and its action. You can't do the same for romance. I prefer something without teen angst ala Gundam Seed Fine romance is fine
The closest one to Gundam SEED would be Gundam Wing and/or Tekketsu Orphan As for action w/ no romance, atm the ones that I could think of are Getter Robo series, Voltes V, Mazinkaiser SKL & One-Punch Man
Watch gintama, it might not be what you're looking for... but you won't regret it. Alternatively Code Geass seems to fit what you're looking for, and it's one of the best anime ever. I cannot explain it's magnificence in a way that does it justice, so I'll just settle for amazing.
I don't hate Gundam SEED but in my opinion Iron-Blooded Orphan is way above SEED. It was really well done.
If you need romance imagine Tanya and the colonel together. It'll be fine well in that case I can do more than just one Well without romance I'd suggest Re:Zero (Just think of the romance as a safety blanket for subaru) with romance there isn't much but in terms of quality or similar stories then there isn't much to recommend My best recommendation is alderman on the sky another would be Fate/zero but its not very close in story to any mentioned so far. Gundam Wing and Iron blood orphans are quality Gundam series that I really didn't expect to appreciate. Gundam Seed has a lot of issues but its not horrible
Could never get into Gintama and trust me I tried, years ago and recently Code Geass, I promised a certain pretty lady to never watch it
For some reason, I feel Violet Evergarden is fairly similar, while also being pretty different. That being said, it's like my now number one fav anime, so I just want to go around recommending it. But it does have a former child soldier (emotionless, a bit different from Tanya). Well, she's already retired and become someone who writes letters for people though. The feels are real. And there's not really any action, but some moving and beautiful scenes. Still, idk, I think the setting is a bit similar, minus the magic and sorcerers and stuff. I'm currently more into shoujo and fluffy slice of life manga/anime right now, so I probably can't recommend anything that's remotely similar to Youjo Senki aside from that. But yeah. Gotta spread the love for Violet Evergarden yo.
Umm... hate to poison your mind, but about 30% of the time that leads to bromance or outright yaoi... depending on the source >_< On a more serious note, how about Drifters? (war, homicidal psycho mc)
A bit of offtopic... While the YS anime isn't bad, I think it presents a bit of a different idea than the novel – it somehow feels like it's trying to make Tanya more "evil" than she actually is. A lot of depth is lost in anime adaptation, though, it's problem with all ecranisations.