The main protagonist is the Baron Philippe de Sucy, who was the "Great Napoleonic Army" and enjoyed the drama of the Battle of Berezina in 1812 in Russia, where in addition to the militaite defeat, Philippe de Sucy knew a love defeat, I say no more ...
Then we find ourselves in 1819 when Philippe de Sucy has remained in the Army that we are now under the Legitimist Bourbon Restoration and it is in this context that also takes place much of the outcome.
Between Army, political and Love periods, we can clearly get in "Farewell" with "Colonel Chabert" since we are in the presence of officers who admired the Napoleonic Empire and crashed at the same time as him (in the sentimental nostalgia for an elsewhere once made the Restoration).
NB: Note that Balzac was legitimist (so for the Restoration 1815-1830) and at the same time he admired the regime of his childhood that was the First Empire (1804-1815). Then in other novels like "La Peau de Chagrin," he criticize -under a form voilée- the July Monarchy (1830-1848) he perceived as the summit of bourgeois illusion.