The memos supposedly revealing 1st Lt. Bush was AWOL and a bad soldier written by Lt. Col. Killian were addressed "To file", meaning they weren't actually sent to anyone, just filed in Lt. Col Killian's personal file. One of the memos dated 18 aug 1973 is titled "CYA" (link is to Powerline). It documents how (then retired) General Staudt pressuring the Lt. Col. to "sugarcoat" a review for 1st. Lt. Bush.
So let's get this straight. A retired General no longer affiliated with the National Guard (yes, that is redundant) is pressuring a commanding officer to falsify a report about a 1st Lt. That commanding officer is so concerned about the ethics of the situation, he agrees to accomodate the retired General then creates evidence his report was false by documenting he backdated the report and omitted a rating in lieu of giving a presumably bad rating. The Lt. Col. then calls that "CYA" (cover your ass).
Instead of filing a memo to self, a commanding officer would include justification for not giving a rating in the report itself. The reasoning for writing the memo doesn't follow. The implied logic is that if ever asked about the report, the Lt. Col. could claim "I filed a false report but I was pressured to do it." That excuse would not relieve him of the responsibility of making a false report. The memo would only prove he did so knowingly.
Was he a fool or is the memo a forgery?