8 Corps?

[Manassas 1861]

Historian Frank O'Reilly in his book on Fredericksburg says the Yanks had 8 corps under Burnside. But Burnside had grouped 6 corps in 3 grand divisions. Imn familiar with the AoP ever having 8 corps. Did they really have 8 corps at Fredericksburg? If so, why weren't the other 2 not put into grand divisions?

 

[AlexPensFan86]

Yes, the 11th and 12 Corps were part of the army, but not engaged at Fredericksburg. I believe they were stationed near Aquia Creek and grouped as the Reserve Grand Division under Sigel.