Maj. Powell's Response
The letter's troubling allegations were not well received at Americal headquarters. Maj. Powell undertook the assignment to review Glen's letter, but did so without questioning Glen or assigning anyone else to talk with him. Powell simply accepted a claim from Glen's superior officer that Glen was not close enough to the front lines to know what he was writing about, an assertion Glen denies.
After that cursory investigation, Powell drafted a response on Dec. 13, 1968. He admitted to no pattern of wrongdoing. Powell claimed that U.S. soldiers in Vietnam were taught to treat Vietnamese courteously and respectfully. The Americal troops also had gone through an hour-long course on how to treat prisoners of war under the Geneva Conventions, Powell noted.
"There may be isolated cases of mistreatment of civilians and POWs," Powell wrote in 1968. But "this by no means reflects the general attitude throughout the Division." Indeed, Powell's memo faulted Glen for not complaining earlier and for failing to be more specific in his letter.
for more on the Powell/My Lai connection
https://consortiumnews.com/archive/colin3.html