Research and the Changes It Can Bring
I first sent my novel Battle for the Wastelands to a publisher last September and when I didn't hear back within six months, I was told I could resubmit (since I'd made changes) and due to the delay, could submit to another publisher too. I sent out the then-current draft to the two publishers and to a few agents as well, one of whom wanted the first three chapters and a detailed synopsis. Back to waiting.
In the meantime, I'd found a couple library books that were interesting and could be useful to my writing. The first book is Empire of the Summer Moon, which is a history of the Comanche Indians, while the second is City of Fortune, a history of the city of Venice during its heyday as a maritime republic.
In the Wastelands world, the surviving armies of the Merrill dynasty and various civilian refugees eke out a precarious existence on the fringes of the Northlands, periodically raiding the villainous Flesh-Eaters for supplies and living in refugee camps. Their existence resembles the Comanche, except their reliance on agriculture reduces their mobility. This makes them more vulnerable to being run down and killed, plus their enemies possess squadrons of airships that make it easier to spot them.
However, Empire references how one of the defenses the Comanche enjoyed against Spanish/Mexican and American imperialism was the Llano Estacado. The vastness and hostility of this terrain made gave the Comanche a refuge that wasn't even penetrated by their (non-Indian) enemies until the later 19th Century.
This necessitated a revision of the world's geography--there's a new region called "the high plains" southwest of protagonist Andrew Sutter's hometown of Carroll Town where due to the hostile geography, the Merrill remnant is safe and even has a base for raiding. I'm going to need to sit down with a pencil and piece of copy paper to map out the geography again. I already had the river valley of Carroll Town transition to badlands to the Iron Desert itself realistically; now I need to make sure the badlands (north) and desert (south) transition into the high plains further west as well. I'll also need to explain why the high plains are located where they are. Right now, I'm thinking some kind of tectonic or volcanic action forced the land upward into slightly cooler altitudes and produced an occasional spring to allow for more vegetation than the badlands or the desert.
Meanwhile, City of Fortune provided an explanation for why even though centuries have passed since the end of the Old World, there has been so little contact between the Northlands and the peoples below the Iron Desert, to the point many people believe the Iron Desert goes on forever. There is a western ocean and that would allow for ships to bypass the desert. I handwaved that in the earlier drafts by saying that warfare before Grendel united the lands between the mountains and the deserts and the seas consumed resources that could be spent on trade and exploration. However, even during the Dark Ages, sea trade and travel in the former lands of the Western Roman Empire never stopped.
So I added a new polity south of the desert, the city of Everett. They're a mercantile republic like Venice and other Italian cities used to be and they have (and enforce) a monopoly on trade between north and south. The Northlands, so recently united, does not have a large fleet and breaking Everett's monopoly will take a long war in a field that Grendel and friends have little experience. However, the trickle of trade across the Iron Desert shows it can be crossed, so Grendel's plan to expand his empire south of the desert, in addition to providing his warlords something to do, also serves to break Everett's monopoly on large-scale trade. It can even force them into an alliance--having lost their monopoly, they'll need to join Grendel in expansion in the south to avoid falling into irrelevance.
That research didn't require many changes to the first novel, but required more changes to later books that cover Grendel's war in the south and the eventual return to the Northlands. There will be an entirely new military campaign that Andrew and Grendel will not be involved in that could be the domain of spinoff novellas and even additional novels. Think the Ender's Shadow series that follows the side-character Bean from Ender's Game. Had Tolkien been inclined, he could have written additional novels dealing with the other theaters of the War of the Ring--the books primarily cover the war between Sauron and Gondor in the south, but additional material references Sauron's armies sacking Dale and besieging the Dwarven kingdom of the Lonely Mountain and battling the Elves as well. The latter could have been a novel centering on Galadriel and her kin much like how the canonical novels centered on the Fellowship of the Ring.
These changes might be a surprise for the editors if they accept the book and send me a list of rewrites that ignore these issues. However, nothing is canon until it's printed. Better that I deal with these issues now rather than realize them after the first book is available. And the introduction of Everett has provided a massive opportunity for spinoffs and even licensed fiction.
Just got to sell the first one. Just got to sell the first one.