Broadly, moving away from the initial focus on military glory to a more philosophical and literary point of view, a focus on the cultural and intellectual achievements of humanity rather than the military and political stuff he idolized before (which also explains his relative indifference to the politics as the timeline draws near the barricades, compared to his strong political beliefs earlier. It's not just Cosette). There's probably some deeper stuff to unpack there, but that's what comes to mind at first.
(I love Job. "I will maintain my ways before him...")
Apparently some of Marius's struggles are based on Hugo's efforts to start a writing career in opposition to the wishes of his father the general (who controlled the purse strings), who wanted Hugo to go into law. Interestingly, one of his brothers, Abel Hugo became a historian who wrote a lot about Napoleon and Spain. Marengo
was a major victory by Napoleon over the Austrians in 1800, forcing them out of Italy. It took place just 10 miles from my ancestral town, so I tried to go see the museum when there in June, but it was closed. I saw a little of the battlefield, though.
It's not mentioned in the initial description of Marius's father's career, but it is mentioned when Marius thinks of his father's reaction before the barricades. "...it was because, coming from Marengo and Friedland, [the sword] did not wish to go to the Rue de la Chanvrerie..." I don't know if that was meant to be symbolic or to imply that Pontmercy was actually there.
Here day embraces night, and says: I will die with you and you will be reborn with me. From the heavy embrace of all desolations springs faith.
The real name of devotion is disinterestedness.