As you can (hopefully) read in the briefing, the Soviets are retreating. If you get to this scenario in the campaign, you have already completed the 2nd Kharkov and Voronezh scenarios.
Axis theater assets:
Note that theatre assets are all available every turn, although that doesn't mean you can use them every turn as for certain assets, certain conditions have to be met.
The Stuka: The Axis get 4 air strikes, which can cause anything from 0 losses, to up to 3 suppressed steps or up to 2 KIA'ed steps. Note the "or", as you can't cause both suppressed steps and KIA's with the same air strike. There's nothing stopping you from bombing a particular unit 4 times, though.
The fuel drums: supply. This asset can be applied to a supply source and will increase the supply radius/burst of that supply point by 1 movement point. In a ~medium sized scenario like Fall Blau, you have supply sources at various edges of the map and which supply source's burst you increase is a very important decision.
The bridge: rivers can be bridged at certain points. Bridges become functional the turn after you place them. This is one of the assets that you in many cases can't use every turn, at least in a practical manner. In some scenarios you can just bridge random rivers in the rear if you feel like it.
The fuel drum on a parachute: air supply. This can be used to restore supply to an out of supply unit, anywhere on the map. This is usually needed to keep your spearhead in supply, and as with the other supply-related theatre asset, deciding which unit(s) gets fully supplied is an important decision.
Soviet theater assets:
Partisans: the Soviets can convert any hex that is not an objective, urban, doesn't include a railroad and isn't in the ZOC of an Axis units to their side. Clever use of this asset can be a game changer.
WitE Alpha tester
Panzer Corps Beta tester
Unity of Command scenario designer