Many of us like playing and running sandbox campaigns, while many excellent blog posts have been written on this topic(like the great series of posts by Robert S. Conley), they mainly are about fantasy and sci-fi(or sci-fantasy) sandboxes. While many of the proposed guidelines for running and creating sandboxes are universal, still some of them does not apply to the historical sandboxes. In this post I'd like to propose a method, few suggestions how to create and run historical sandboxes without much effort.
First we must choose the scale of the sandbox(i.e. how big the area to explore will be), as a general rule - the smaller area the higher historical accuracy would be needed. So e.g. I'd like to run a sandbox camapign during thirty years war, in general lets say. The map of whole Europe will suffice with major cities and places important to this time period. Less important things like smaller settlements could be quite generic, only giving detail to the major ones. This type would be similar to pointcrawl presented by Chris Kutalik. On the other side of this continuum would be a local sandbox, where sure amount of historical detail would be needed. Both have merits and flaws.
While former might seem a bit overwhelming at first, It will need just a brief write up about major countries/regions/specific places. The advantage of this type of sandbox is diversity of places to visit/explore, where when players get bored they may move to another place completely different from the previous one, without wasting the gm's effort on history research.
While I've played both types I've worked out a third type. This one is in fact a group of small sandboxes placed on one map. This one seems to be the best in terms of research time/gameplay time proportion. On the latter I'd like to focus.
First I make a general hex map with 24 miles per hex.
Second a home base sandbox should be established. I usually work out 7 hexes with a town at the center hex and some smaller settlements scattered around the peripheral hexes. Than I move on to the next small sandbox repeating the procedure above 3-5 times. Of course doing some history research about those places in the meanwhile. This size of mini sandboxes is IMHO the best to make the area historically accurate without much effort.
What I'll do with the space between the small sandboxes you may ask? I simply make few encounter tables(with period-appoprieate entries) and draw some generic maps of villages and towns. And that's it. Enough to make a convincible background while not overdoing it.
That's the way I run my Cossacks & Tartars campaigns.