External conflict on its own rarely stands up as being big enough, emotional enough or important enough. Yes, external factors are important in keeping a story moving, but internal factors are the driving force behind character arc and development, and our pathways to making two-dimensional, imaginary characters human. Real.
When writing a large cast, you have to know your characters really well. More importantly than that, however, you have to know how they interact with one another. Here are two exercises you, as an author, can do to ensure your characters are rounded and fully-developed before they ever hit the pages of your book.