First, you always spy.
Second, you monitor public information to determine enemy tactics and develop wargames around those strategies.
For instance, anti-aircraft strategies against the USA changed radically as the USA launched preliminary drones to set off Iraqi radar stations then launched cruise missiles against all known pings.
Spies are so common all over the world, they called them diplomats and gave them their own offices.
War gaming, which is basically thought experiements with some rules and writing down results.
If red team had this stuff and blue team has that stuff what would you attack and how would you defend it. If you lost it what would you do to make up for it?
The art of war is extremely complex and there is no way to cover everything in one Lemmy comment.
However, I can summarize: An attacker or defender simply needs to prevent the opposing side from being able to support a war.
While there are thousands of different things that can support war, it usually boils down to raw manpower, food/supplies, weapons, energy, logistics and communications. Failing to defend, or not having the capability to replenish/repair those things is usually a quick game-over as those items are highly dependent on the other. Anything that supports those key items is a target of the enemy, so those are the things that are stockpiled, fortified or should be rebuilt quickly.
