In 1807 the Saxon Cavalry was dismounted in order to provide horses for dismounted French cavalry. However, these were soon recovered as the French disliked the spirited Saxon steeds.
In 1809 the Saxon contributed a corps to the Confederation of the Rhine and had, at the onset of the War with Russia the following cuirassier regiments :
- in the Guard : the Garde du Corps and the Leib Cuirassier Regiment
- in the line : the "von Zastrow" Cuirassier regiiment
each with a normal strength of 4 squadrons.
I don't know what Keving means with the "König"-regiment - is it the Leib Cuirassiers ?
The Saxon contigent which was required for service with the French Army was known as the IX corps, commanded by Bernadotte, but the Garde du Corps had only 2 squadrons, while the Leib Cuirassier regiment had their 4 squadrons. The "von Zastrow" regiment was left behin after providing mounts for the other regiments.