In what way is history intermingled with literature in this chapter?

This section functions solely to give a detailed history of March's early years with Marmee. It is clear that the relationship was fueled by passion. On their first night alone together, both lost their virginities in the woods, and it is in insinuated that Marmee became pregnant that very night. When the reader learns this after witnessing March's interaction with Grace in the previous chapter, it becomes clear that March doesn't think before he acts.