BIRDS OF PREY was the first novel I tried to write. It was a very long time before I succeeded, but I think in this case the wait was worth it.
While I was still in law school I got and read the two-volume Teubner (Latin text only) edition of the so-called Scriptores Historiae Augustae, the Augustan Histories. This is a collection of lives of the later emperors (Hadrian through Numerian), purportedly by many contemporary authors but probably by one man of much later (5th century?) date with political axes to grind. While the SHA is in many respects a fictional text, it does incorporate material from books that haven't survived--and is, for my purposes as a writer, very evocative.
I became interested in the so-called Third Century Crisis: the point at which the Roman Empire shattered and almost ended, only to be pulled back by Diocletian to further centuries of flowering. I got some notions--scenes only, but vivid scenes--and thought maybe I could turn them into a novel.
Not then I couldn't. I wrote a chapter or two, then stalled out. I didn't know how to plot yet, and I didn't know that I had to plot. (There are various ways to write a novel. The way that works for me is to plot it out in detail before I start the actual writing.) That first attempt occurred before I was drafted in 1968.
I made several more tries at writing a novel in the years following. Not only did I write a few chapters (probably the same few chapters) of my 3d century fantasy (it got a title this time: The Warm Summer Rain), I did a time travel YA (which I actually completed; Karl Wagner read it and heaped no-doubt deserved scorn on it. No one else is likely to read it during my lifetime) and some chapters of a Roman historical which have a degree of merit. They weren't a novel, but the writing was vivid.
There matters rested till andy offutt asked me to plot a novel for him (see my comments on The Dragon Lord) and I learned what a novel was. (Incidentally, if it seems to you that there were easier ways to get where I was going, I think you're right. This is the way I took, but I'd never recommend that another would-be writer try to model him- or herself on me.) I wrote The Dragon Lord, then wrote The Forlorn Hope for Ace (see the comments on why Ace didn't publish it) and Skyripper in response to a call from Jim Baen who needed material for Tor Books, which Tom Doherty had just founded and hired him to be editorial director of. (There's a story in that too, but I'm not going to tell it. Even for me, some things are water under the bridge.)
After I turned in Skyripper, Jim called again to offer me a two-book contract, a major book and a minor one. I was ready this time to write the 3d century novel; it became Birds of Prey. (The minor one was Cross the Stars; not in fact as minor as I thought it was going to be. And the day after that call, Jim called back and made it a three-book contract, the third being Bridgehead. It was an exciting time to be alive--but you know, they all are if you've got the spirit to understand that.)
The title came from a Kipling poem, "The Birds of Prey" March, a perfectly-realized description of soldiers boarding a troopship for overseas deployment. The refrain, "The Large Birds o' Prey, they will carry us away, and you'll never see your soldiers any more," caught for me the mood of the book I intended to write. Jim didn't tell me that The Warm Summer Rain was the stupidest title he'd ever heard of, but he might have done. (Nowadays he probably would.)
I did a great deal of research into the history of the period (the SHA is mood and incident, not history). Most of it's archeology and conjecture; there really are no first-rate written sources extant. That wasn't an entirely bad thing from my viewpoint. My most valuable single source was a trip to Adana, Turkey, and across Mesopotamia by road to Diyarbakir on the Tigris. That was possible due to my friend Glenn Knight, then US vice-consul in Adana. (I'd originally--that is, in 1968--intended to climax the novel in North Africa; which, oddly enough, we'd visited a couple years before the Turkish trip when Glenn was GSO at the US mission in Algiers)
I wrote Birds of Prey in 1983, about 15 years after my first attempt. I'd learned to plot and I'd learned more about writing (I'm still learning more about writing); but the most important difference had come in the years 1969-71. During that time I got intelligence training from the US Army and was given a close-up view of what war, soldiers, and lands wrecked by catastrophe are really like.
Birds of Prey isn't a perfectly-structured novel, but it's a darned strong and vivid one. It has in it a lot of what I believe is true. I'm proud of the result, and I don't regret that it was a long time coming.