"...60 to 80 percent of the 6th Cavalry Corps were destroyed on June 22 as they struggled to assemble in formation)."
How can most of a cavalry corps be destroyed in a single day? Would they not be able to retreat? Could it have been ambush of a camp?
I'm just confused as to how such a large, mobile force (over 15,000 men) could be nearly destroyed in such a short period of time.
The 6th Cavalry Corps was part of the 10th Army in 1941. Now, I can't actually properly answer your question because the sources I've seen don't entirely agree with the statement that the 6th was largely destroyed trying to assemble in formation.
To my knowledge the 6th was part of an ill fated counter attack towards Hrodna along with the 6th and 11th Mechanized Corps under General Boldin. However, that was launched on June 24th which suggest that the Corps was at least somewhat intact at that point, some 48 hours after it was supposedly destroyed trying to assemble.
This was not a result of NKO Directive No 2 & 3 (ordering at first counter attack against German units on soviet soil and subsequently a general counter offensive with no regards for borders) but rather an attempt to prevent the entire front from being encircled. The 6th Cavalry Corps was indeed destroyed in the Bialystok-Minsk offensive but not, at least according to Glantz in Barbarossa: Hitler's invasion of Russia 1941, on June 22 while trying to assemble.