I know spies were helpful, but the logistics of it baffle me. In the movies, they always seem to meet up with all their units facing one another in perfect formation. But, in real life, i never got how they found each other over the huge expanses of land without any modern reconnaissance methods.
You can read the whole post here, where I've address it previously.
The long and the short of it is that armies do not exist to fight one another, they exist to secure objectives. Therefore one or more armies are on the move in pursuit of an objective and the other army attempts to block them. They are likely to run into one another based on inferences made from scouts and the only logical paths that armies can go.
The old adage is that battles take place along the lines of communication. This is as logical and simple a concept as you can imagine. It's easier to communicate with the people you need to communicate with, and there's a reason people use that path, well, for communication, so typically speaking you're going to see battles take place around areas that are easy and routinely traveled. Not necessarily on those sites, but around them. Armies can march through rough, rugged, shithole terrain (see Hannibal's march through the swamps to avoid engaging the Roman army, Alexander, B. (1993) How Great Generals Win p.41) but typically speaking this was dangerous, as seen when Hannibal lost a number of his men by risking those very same swamps. So typically, an army wants to use roads, rail, paths, trails, whatever guarantees their destination and ultimately makes life easier to keep a cohesive unit.
Is the first excerpt but I highly recommend reading the whole thing for a more in depth explanation of your answer.
I'd also be happy to answer any additional questions.
Also to the others: I know, Trebia, it's just too late to edit that thread, lol.