Stennis wrote the first Senate ethics code, and was the first chairman of the Senate Ethics Committee. In August 1965, Stennis protested the Johnson administration's emergency supplemental appropriation request for the Vietnam War. In August 1967, Stennis advocated for an expansion of bombing North Vietnam to hasten what he believed would be the war's conclusion, adding that either restrictions or a pause could be a mistake. In July 1969, Stennis proposed dividing South Vietnam into two zones and one would be used for the United States to attempt ending the war. In December, Stennis supported the creation of a special commission by President Nixon with the intent of investigating alleged Vietnamese civilian slayings at the hands of American soldiers.