: Paradis must spend 50 years modernizing their military to compete with the world.
: In the present day, we see the tragic outcome. Historia is shown pregnant and despondent, seemingly having accepted a fate she never wanted. 10 : A Sound Argument
: In a poignant flashback, Eren Jaeger vehemently refuses to let Historia be used as a "breeding tool". : Paradis must spend 50 years modernizing their
: A small-scale display of the Wall Titans' power to deter world invasion. : In a poignant flashback, Eren Jaeger vehemently
If you are referring to the episode " A Sound Argument " (Season 4, Episode 10), it is a story centered on the heavy burden of duty and the erosion of hope.
The "sound argument" of the title refers to the cold logic that sacrificing one individual (Historia) is a necessary evil to save the nation.