Men with Steel Faces is an edited movie version of the serial Phantom Empire, which stars Gene Autry as — who else? — Gene Autry, a singing cowboy who also has a Radio Ranch where he broadcasts a show every day and also has a dude ranch for kids where Frankie (Frankie Darro) and Betsy Baxter (Betsy King Ross lead the Junior Thunder Riders.
All three of them are kidnapped by soldiers from the advanced underground empire of Murania — justified and ancient — who have laser guns, robots and an evil queen named Queen Tika. Meanwhile, Professor Beetson and his gang are trying to steal all of the riches of Murania and double meanwhile, there’s a rebellion looking to overthrow the evil empire.
This serial went on to inspire the NBC series Cliffhangers!, which had a sequence called The Secret Empire. There’s also the Fred Olen Ray movie The Phantom Empire which is directly inspired by this, as are the legends of the Shavers*, which you can learn more about in the movie Beyond Lemuria. Other movies that have an under the world army include The Lost City, which pretty much outright steals from this serial and The Mole People.
I love the idea of cowboys interacting with futuristic science fiction and celebrate any movie that makes it happen again, even poor ones like Cowboys vs. Aliens.
*The Shaver Mystery was created — or discovered — by factory worker Richard Shaver who was able to hear within the center of the Earth and wrote to the magazine Amazing Stories and suddenly, that entire pulp was all about creatures and civilizations that existed within the Earth that are quite a bit like Phantom Empire. Then again, this movie’s writer Wallace MacDonald got the idea for this story when he was getting gas at the dentist.