I just finished my first game (1939/42 scenario) of Third Reich PC.
It is fun, in a retro sort of way. The AI isn't terrible, but the difficulty setting is essentially just multiplying the computer player's resources.
I let the computer play the Axis, with the AI set to the maximum difficulty. It turns out this equates to:
1) Double economic resources (BRPs) for AI major powers
2) Something like double the force pools for AI major powers. In the 3rd Reich family of games, the force pools are extremely important in terms of tuning. When we were developing the research system for A3R/Rising Sun/A World at War, even a couple extra units in the first part of the game could have significant effects. Suffice it to say, we never considered anything like doubling them...
3) The player major powers get 0% BRP growth rate. This would REALLY make a campaign game on this setting tough for an Allied player (and probably an Axis player as well). The US and Russian economies in the original Third Reich only expand by the growth mechanism, so setting their growth rates to zero means they will be stuck around 1939 levels even in the late war. Major handicap there. (Advanced Third Reich and A World at War have much more robust models of Russian and American economic expansion).
Anyway, in my game, I made a very strong British commitment to defending France. I vaguely recall that when I played the PC game shortly after it came out, it could not conquer a very strongly-defended France, but in this game, it did finally take out France in Winter 1940. British losses were light, and both Britain and Egypt were pretty well defended the turn after France fell. I wasn't really looking to take chances, as I was still re-learning the rules, and just wanted to see what the AI could do.
The computer player invaded Russia in Spring 1941, which is the normal turn. I had a reasonable Russian defense set up, and the Germans made progress slowly. The scenario victory conditions just depend on the number of objectives controlled, and I had the number required for a decisive victory and a fairly good position at the end of my Fall 41 turn. The Axis can't take an offensive in the first winter, so I figured I was in good shape.
Unfortunately, I forgot to keep an eye on the BRP levels. At the start of Winter 41, Allied BRP totals were slightly higher than the Axis, and I got a completely unexpected and unwanted Fall/Winter double turn, which inevitably led to a Winter/Spring return double move for the Axis. This made things much more iffy. Against a human opponent, giving up a double-turn then would have been "game over".
I survived the double-turn, but my defenses going into the final turn (Summer 42) were really falling apart. I still (barely) had a Decisive, but there were a lot of objectives (Dnepropetrovsk, Kharkov and Smolensk practically on the front line, plus Moscow, Leningrad and Maikop requiring at least some defensive screen) at risk, and letting the Axis take and keep even one of them would have left me to settle with an extremely embarrassing Tactical victory instead.
The AI took Smolensk on their last turn, but Axis attacks ran into heavy losses along the whole front. Only a single panzer corps was left in Smolensk (8 defense) and I was able to scrape up 12 attack factors for a good (win 5/6) 1:1 counter-attack on my last turn, which retook the objective (and the Decisive).