Legend of the Galactic Heroes (1988)

If you care about strategy at fleet scale, this is the one. The Galactic Empire and the Free Planets Alliance are locked in a long war, and the story follows two rival commanders, Reinhard von Lohengramm and Yang Wen-li, as they rise on opposite sides. The campaigns are battles of planning and nerve between two very different minds, and the politics behind each one gets equal time. It is a commitment: the anime, released between 1988 and 1997, runs 110 episodes, adapted from Yoshiki Tanaka's ten novels. The 2018 Die Neue These by Production I.G is a separate, newer adaptation if dated animation puts you off.