 If you liked
Seikai no Senki
|
 ...then you might like
Ginga Eiyuu Densetsu
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Both space war epics dealing with empires and nations, seriously examining social structures and dueling philosophies. Both do their best to seem realistic even while set in a sci-fi future; No mecha.
Large scale space battles and a focus on building an epic science fiction world are shared points. There is plenty of exposition and calm discussion of tactics. You will also experience the outdated, yet fitting and sometimes beautiful animation style. Finally, both shows challenge the view that democracies are the superior form of government.
Note that Seikai no Senki is considerably smaller in episode and character count. It is the sequel to Seikei no Monshou. While a great anime itself, watching Seikei no Monshou first is not strictly needed.