From Riehn

1st Western Army  Barclay de Tolly
I, II, II, IV, V (Guard), VI Inf Corps
I, II, III Cav Corps
150 battalions,  132 squadrons,  18 Cossack Regts, 49 batteries
104,250 men, 7000 cossacks, 558 guns

2nd Western Army  Bagration
VII, VIII Inf Corps
IV Cav Corps
46 battalions, 52 squadrons, 9 cossack regts, 18 batteries
33,000 men, 4000 cossacks, 216 guns

3rd (Reserve) Army  Tormassov
2 inf corp, 1 cav corp
54 battalions, 76 squadrons, 9 cossack regt, 14 batteries
38,000 men, 4000 cossacks, 164 guns

Each corps was to include 2 inf div and 1 lt. cav regt.
2 corps had a cuirassier div instead of lt cav regt.

each battalion approx 500 men
each squadron approx 125 horses

Shortly before the battle of Borodino, the cav regt and cuir div
were detatched from the inf corps to reinforce cav corps.  Also,
most corps art was stripped out to form a stronger art reserve.