Anime
Area 88 (80s OVA series, not the 00s TV series) - A good war drama that shows how war can change a person, with it being one of the rare examples of an open ending elevating the work.
Planetes - A slice of life series done right with it providing a unique setting that balances between the awe of space and the banality of office work with well fleshed out characters.
Princess Tutu - Despite its name and girly appearance, that's mainly a deception. After a certain point, it becomes apparent that it's a deconstruction of the Mahou Shoujo sub-genre and features its cast both figuratively and literally going from archetypes to complete characters as well as some of the most well utilised 4th wall breaks in anime. Whilst MAL says it's 38 episodes, it actually fits your criteria as those after episode 13 with the exception of the finale were originally aired as 12 minute episodes, making it more accurate to say it's 26 episodes.
Takarajima - A retelling of the classic novel Treasure Island. Whether you've read and like the novel or are only vaguely familiar with it, the series has its merit in watching it primarily due to its unique take on John Silver by adding some more to his character than the original novel.
Zegapain - Essentially The Matrix with mechas and a more consistent script. It can be slow at times with how much time it provides to a high school setting of all things, but if you've seen The Matrix and like its themes, then you'll probably like Zegapain.
Mobile Suit Gundam - The original series doesn't really meet your requirements due to being 43 episodes. However, the movie trilogy provides a good way of being introduced to the franchise and is actually treat as canon to later instalments and spinoffs instead of the original tv series, so these three films (Mobile Suit Gundam I, II: Soldiers of Sorrow and III: Encounters in Space) should make a good introduction into the long running war drama in space if wanting to see if it's your kind of thing. If not feeling like continuing the franchise further from the movie trilogy, I'd at least recommend watching the spinoff 0080: War in the Pocket after you finish them.
