The machine gun and trench warfare forced the development of the tank.

Once aircraft became military useful, battleships were rapidly vulnerable to aircraft and hence aircraft carriers.

I can imagine replacing naval mines with normally-quiescent remote-triggered torpedoes that are scattered on the seafloor a decade in advance.

How effective are troops against 3D printed drones designed to mimic animals (including birds), but which have a short-range firearm and some computer vision? Or engineered mosquitoes with the bare minimum of remote control, perhaps similar to the "cyborg cockroach" kits that have been on sale for about 9 years now? (Or just weaponise those 'roaches…)

What happens if you can predict what a command officer will say, use an AI to fake a their voice before they've spoken, and interfere with the communications to give misleading orders in the heat of combat? Doesn't even need to be a big change to the orders to alter the outcome.

(Obviously everything I've thought of in 5 minutes, the actual military will have categorised into "haha no" and "let's wargame this scenario"; I assume mostly the former).