Conclusion: They’re up to something...! (LOL!)
If you recall, the Union instructions said, specifically:
Left Wing -
XII to one mile N, VI and Couch (Franklin) to one mile NE, II to one mile SE of Ijamsville
Mac in charge of whole force
Averell to NE of Urbana, keep CS cav from intervening (avoid battle with infantry)
No attack though clearly I threaten one. I want to see what he does.
Now, here's a quick model of what an attack might have looked like, if attacks at good odds had been permitted...
Units close up on Ijamsville and McClellan moves to Franklin.
Franklin launches assault on Ijamsville, dr 4 vs. initiative value 6: 2 units go in (Smith, Slocum, 24 manpower and 6 batteries)
McClellan upgrades to grand assault? dr 6 - fails
Manpower: 24 attacker, 6 defender (+3 to attacker dice roll)
Type: assault (+1 to attacker dice roll)
Artillery: 6 batteries attacking, 4 defending (no modifier)
Tactics: Jackson (with JR Jones) is defensive 4, Franklin is offensive 3 (-1 to attacker dice roll)
Flanks: All 6 hexes around JR Jones are in Union zone of control, +4; two of them are occupied by Confederates, so reduce to +2 overall
No terrain modifiers
Result: Manpower +3 type +1 tactics -1 flank +2, overall bonus to attacker dice roll +5
Attacker dr 2, defender dr 3
Defender 1DR, attacker 1fa
JR Jones is routed out of Ijamsville at a cost of 500 casualties on both sides (falls back to Slabtown), Smith and Slocum occupy Ijamsville and will be tired the next day
Sumner launches assault on McLaws, dr 3 vs initiative value 6: all of 2nd Corps goes in (34 manpower and 8 batteries)
Manpower: 34 vs 7, +3 to attacker dice roll
Assault, +1 to attacker dice roll
Artillery: 8 batteries attacking, 3 defending, but the terrain is Rough (so no terrain modifier)
Tactics: Sumner and McLaws are evenly matched
Flanks: all 6 hexes around McLaws are in Union zone of control, +4; one of them is forest, so reduce to +3 overall
Result: Manpower +3 assault +1 flank +3, overall bonus to attacker dice roll 7
Attacker dr 3, defender dr 5
Defender 2DR, attacker 1Ea
McLaws is routed at a cost of 1000 casualties to his division and 500 to Sumner's corps
McLaws' only paths of retreat involve going cross country, another 500 casualties
Retreats to Slabtown
The result of this would thus be that two Union corps (6th and 2nd) would be tired by their exertions, and about 1,000 Union casualties - versus 2,000 Confederate ones and two of the Confederate divisions on that flank exhausted.
You might also note that the Union's dice rolls here were at no point better than average; even with poor rolls this is what happened!