Here's the situation in Serbia. It's the first week of September and there's been 4 turns so far. No much happening for me yet as I'm seeing 1 Serbia army opposing me, with probably another Army in FOW. This turn I get a number of mountain corp. This is another big change. There aren't infantry divisions (or mountain divisions), there's corps (at least for right now, never played the mod so not sure how unit builds expand over time). Purchases (right now) are at the Corp level and for the moment, you can only purchase reserve Corp, which come without any artillery (6 brigades and 1 element of officers), and you can purchase medium artillery. Another big change is that it requires officers to build new units and get replacements. Officers are not leaders, but another element added to each corp. AH is weak on building officers, which is why there's an officer "factory" that may be built in October onwards.
A head on attack will be a nightmare of losses. MTSG has changed as well, based on 20% multiplied by strat rating + 20% for being adjacent to battle and more bonuses if next to or under GHQ. Since my GHQ is locked for another month and AH leaders are pretty much horrible across the board, Belgrade will be a difficult nut to crack, so I'm going to stretch him out a bit. My German ally is sending some forces down to help take Belgrade.
Another big change is that anything with wheels cannot move into regions without roads or rails. This include supply trains. On the right flank will be a Kallaverie Korp, but it can't have supply trains with it. On the left flank, the 6th Army along with a Mountain Corp will attempt to push to the east. Doubtful it will get far, but the goal is to stretch the Serbians and open an opportunity for Belgrade. Currently, the Serbians have a Corp in Belgrade, another Corp opposing the 6th Army on the right flank. An Army (800 PWR) in Loznica and an unknown amount (possibly Army or 2 Corps) in between Loznica and Belgrade.