Elder B. H. Roberts was a chaplain in the United States Armed Forces during World War I. The war finally drew to a close, and the peace treaty was signed on 11 November 1918. Two weeks later, on Thanksgiving Day, the American soldiers were gathered together "in one grand Thanksgiving service."
"The large attendance included high-ranking military officers and the services were conducted by the chaplains, who were seated on the grandstand.
"Elder Roberts was relegated to one of the rear seats. He had not been asked in advance to participate on the program, therefore, it was with great surprise that he heard the chaplain in charge announce: 'Elder Roberts, the Mormon chaplain from Utah, will now step up and read the Thanksgiving Psalm.'
"Elder Roberts had never heard of the Thanksgiving Psalm but, hiding his personal embarrassment and possible impending embarrassment to the Church, he arose and walked to the podium, not knowing what he should say.
"Years later he testified that, during the long walk to the front, he distinctly heard an audible voice announce: ''The 100th Psalm.' It was as clear as though another person had spoken at his side.
"Elder Roberts faced the crowd, paused, then opened his Bible and read Psalm 100....
"After Brother Roberts had closed his Bible and was returning to his seat, he noticed that his fellow chaplains refused to look at him; their eyes were immovably fixed on the floor.
"It was then he realized that his part on the program had been a deliberate attempt to embarrass him, the Church and the priesthood. He acknowledged the help which he had received from the Lord in his moment of need and, when he returned to his tent that night, he checked the Book of Psalms, discovering that the 100th Psalm contained the most pertinent and appropriate sentiments on Thanksgiving."

("Inspiration, Key to Thanksgiving Psalm," Church News, 22 Nov. 1975, p. 12)