Chancellorsville is unique among the published scenarios in Battle Cry in that neither army has a presence in all three sections of the battlefield. Indeed, the Federals, except for one unit, are all concentrated in the center section.
Hooker's boys also labor under the handicap of having Hooker as the boss, so they have only a three-card hand, compared to the Rebel 5-card hand. As a matter of fact, the only real advantage the Union forces have is numbers, with 12 units compared to the Rebel eight. But even here, the federals have a disadvantage because their army is not well-balanced, having no cavalry unit.
The bottom line of all this is that, at the start of the game, fully 32 of the 60 cards in the deck are completely useless or will result in a single unit being able to move. On the plus side, there are five cards that can be really devastating for the Federals to play if they get them, the All-Out Offensive and, almost as good, the two Force March cards. The Fore and Hold Position is also pretty powerful. All five of these cards will allow all, or nearly all, of the Federal units to battle in a single turn.
The problem for the Union player is, with a mere 3-card-hand, chances aren't all that good you'll get one of those five cards (1/12th of the deck) while it's almost certain you'll have one or more cards that you can't use. Even the Counter-attack card may not help, because the Confederate player can be careful to only activate units in a section where the Federals don't have a presence.
While the Rebels start with 14 cards they can't use (12 Center Section Probe, Attack or Skirmish orders and the two Hit and Run cards) they can afford, with a 5-card-hand, to hold onto any center cards for a few turns until they have the need to move into the center section. So there's really just two unusable cards for them in the whole deck.
Given all this, what approach gives the Union player the best chance for a victory?
Battle Cry, like all the Commands & Colors games, doesn't lend itself to "perfect plans." The luck of the card draw means that no plan can be sure of execution, and sometimes the other side may get lucky. A Rebel player at Chancellorsville who confidently starts enveloping the Union force may get a very rude awakening if the Federal player happens to have two of this five killer cards.
But on average the Rebel player is going to be able to be very active, able to dance around with his 8 units, picking at a federal force that may not even have a single usable card in his hand.
From a card management perspective, there's little the federal player can do except play 'em as he draws 'em. If not pressed too hard, the union can "play" a worthless card just to get it out of the hand, but most of the time the critical need will be to act as often as possible. I think the Union player does have an opportunity, if he's single-minded enough to act on it, and that is to concentrate on Stuart's portion of the Confederate army.
There are exactly six flags available on that side of the field (general, artillery and four infantry) and there is one federal unit that starts on the sector boundary and therefore has 10 more cards available than the rest of the Union force. There's a chance, if the cards cooperate, to concentrate all 12 federal units against the five Rebels.
It still looks like a challenging scenario for the Union troops, but I think this approach gives the best shot. Critiques welcome.