Even if you don't zoom out, soldiers can still get a fairly good bead on whats going on. Gossip, rumors and just being in the right place at the right time.
But yeah, a good idea would be to study actual wars. Look at how technology (and magic, if you have it) would change not just how people kill eachother, but how they move and how they communicate. These have HUGE impacts on how people fight.
Frex, in the 18th century, people got into lines not just because their muskets were hugely inaccurate, but also because it was the only way to effectively coordinate troop movements in the heat of battle. Even in the civil war, where guns got way more accurate, armies had a huge command structure and system of couriers to run notes back and forth.
Heck, Gettysburg was such a crushing defeat for the South because of communication errors. I mean, everything else wasn't so hot for them, but some people (including me) think that if Lee had better communications and intelligence, he could have either won the battle...or at the very least, not lost it so hard.
Anywho, read a lot. Think a lot. Those are my suggestions.
And do everything Kitty says. BUt that's just general advice.