It took a bit of refactoring, but I managed to get a version of the combat resolution mechanic working. You can now dispatch a Wehrmacht fire team silently with knives using a "Stealth focus" attack.
I consider this a milestone! You can now wander around the map and attack the various challenges, so the core mechanics of the game are in place. There's still a lot of cleanup that needs to happen around it, but the framework I'm using for displaying stuff makes it pretty easy to produce nice looking dialogs.
Above are two screenshots from the gameplay. The topmost one is where a private is choosing what action to take on his turn. The second is that private choosing a challenge to attack. Some challenges require you to have a certain level of "focus" in order to attack them (i.e., it requires a lot more firepower to attack a Panzer tank than it does a lone scout), and the system for enforcing that all is working.
It's not a game yet, but you can kind of see it through the trees!