Roy apparently earns his title as King of the Cowboys by helping out Governor Russell Hicks of Texas track down a nest of Nazi saboteurs who are wreaking havoc across the Lone Star State. Did Congressman Lyndon B. Johnson know about this?
Herbert J. Yates put the best creative minds at Republic Pictures to work on this and they came up with a script that's a combination of The Thirty Nine Steps and This Is My Affair. Like the Robert Taylor MGM classic where he's a secret agent working directly and reporting to President McKinley because McKinley like Governor Hicks can't seem to trust anyone in his official capacity. And like The Thirty Nine Steps the key is Gerald Mohr with a carnival memory act. If you're going to borrow at least Yates felt you should borrow from the best. You can't do too much better than Alfred Hitchcock.
Roy gets a nice group of songs and I particularly liked the fact that he gets to sing I'm An Old Cowhand which in fact he had a hand in introducing seven years earlier. When Roy was just one of the Sons of the Pioneers who also appear in King of the Cowboys he backed Bing Crosby when he introduced the Johnny Mercer classic in Rhythm on the Range. Now Roy's a star and does a nice solo turn accompanying himself on the guitar.
While Republic's other big singing cowboy Gene Autry was off to war, Roy inherited for a while, Smiley Burnette who does his usual comedy bit.
Sadly though the film that gives Roy the title he was forever known by is a badly dated war propaganda flick that simply doesn't wear well or age well. The King had been better served by his subjects at Republic before and after this film. They'd also done worse by him as well.