I could have run such a campaign by setting it at any point in time, I suppose. Donald Featherstone and Donald Bailey both created rich imaginary worlds set contemporarily with the height of the British Colonial period. Tony Bath ran many, many campaigns over the course of several decades in his famous Hyboria fantasy world. But for me, the 18th century is, undeniably, the best choice for this escapade.
Brightly colored uniforms attract my eye and my imagination. I spent many happy hours as a child reading and re-reading well worn copies of the Britains and Prince August catalogs. One of my earliest wargaming purchases was the two-volume Funken uniform guide, "Arms and Uniforms of the Napoleonic War." I've painted many Napoleonic and American Revolution figures over the years, and still enjoy the sight of them on the table. So, choosing a period replete with dashing uniforms was a must.
When it comes to large wargames between embattled armies, I have a strong preference for the three-cornered stool of infantry, cavalry and artillery. I enjoy the interplay of unit tactics between the three arms. The rock/paper/scissors point and counterpoint of three arms (if you'll pardon the deliberate oversimplification). Infantry are numerous and must choose between the more effective firepower of a long, thin line, the advantages of mass and maneuver obtained by forming into dense columns, or the protection from cavalry afforded by square, knowing that either of the latter formations leave them far more vulnerable to the bouncing, spinning iron of cannon fire.
I could have gone back in time, and set my campaign during the Thirty Years War. But the artillery of the day was nearly immobile, and infantry tactics were too much about the push of pikes and too little about maneuver (again, painting with a VERY broad brush). I could have set my campaign further forward in time, during the Crimean or American Civil Wars. But the advent of rapid fire rifles and rifled artillery were changing the character of battle dramatically again and, while interesting in themselves, these changes were too far from what I was seeking.
Which narrowed my choices to the mid- to late-eighteenteenth century (roughly speaking, the Seven Years War and War of Austrian Succession) or the very early nineteenth century (the Napoleonic Wars).
The final considerations I used to narrow my choice were the dual and related needs for an invented land, and armies wearing invented uniforms. A nation unheard of before, but that could fit into the larger historical context without asking too much of the readers' (or my) willing suspension of disbelief. The nation had to be plausible. The uniforms should reflect the period, but avoid being easily identified as belonging to any particular real world nation of the time.
And that ruled out the Napoleonic Wars, for me. All that reading about those wars, over all those years, have left me very, very familiar with the period and cast of national characters. Adding another player to the mix of nations would have been possible...perhaps in the Balkans or a corner of the German states...but harder to swallow than the addition of one more Duchy amid the many, many nation states that made up 18th century Europe. A certain amount of anonymity is possible, that I found lacking in the Napoleonic period.
And the uniforms! I can tell, at a glance, a French shako from a British Stovepipe, and a Russian wide-topped shako from a Spanish grenadier's mitre. Yes, many nations adopted French or British uniforms in their own colors. Yes, I could have gone that route. But to me, my battalions would always evoke a reaction of "Oh, I see, those a French figures painted purple."
By way of contrast, the 18th century armies looked, for the most part, nearly identical. Nearly all wore tricorns of a cut so similar I can't tell them apart in 15mm. Nearly all worn long-tailed coats with turnbacks. Nearly all fielded cuirassiers and hussars and dragoons undistinguishable from each other until the colors of their uniforms could be discerned (and frequently even then!). Which left me with a blank canvas, when it came to uniforms. Choose a uniform coat color, design a national or regimental flag, and the army of the new nation is born.
So, for all of those reasons, my little nation state of Baden-Hundsheim, and their ancestral enemies to the North, the Principality of Formulgala, will reside firmly in the mid-18th century. I can't wait to get started painting the armies of these two new lands.