I, too, remember figuring out a strategy when I was around 11, and never lost a game after that.

It's been a loooong time, and I don't recall all the details. But it revolved around doing probing attacks to determine where the ranks were in the enemy formation, and then having "channels" in my side to move up a soldier that outranked by 1 a targeted attack.

Color me surprised that it would be difficult to write a program to play it.

Most of my setups, though not all, revolved around bombs and strong soldiers held in reserve behind the bombs, sort of a rope-a-dope...sometimes, I'd kill all of their miners before the bombs surrounding the flag could be disarmed which guarantees no quick win for them. There are risks to that, in that the strong pieces can be stuck while the opponent picks off everything else, but even once people knew I regularly did that, I could still win pretty much always, so it's more than a strong opening layout.