This book is two stories on the continuing reincarnations of Julian from the Moon Maid.
The Moon Men
Several years after Julian makes it back to Earth his arch nemesis Orthis arrives with an invasion fleet of Kalkars from the Moon. Julian takes the small defense fleet that Earth has into battle. It is destroyed but not before killing Orthis. The Kalkars are able to conquer Earth with no opposition and implement their form of Socialist government.
Several generations later Julian is reincarnated in Chicago. This future is a very grim place. The Kalkars ineptitude and ignorance have reduced society to a medieval level. Americans are little more than serfs under the Kalkars. Julian 9th lives with his parents and toils for the brutal overlords. One day he rescues a young woman from vicious hellhounds. What follows is the typical Burroughs love story and a failed uprising against the Kalkars.
The Red Hawk
Several generations later and Julian is reincarnated as Red Hawk. Red Hawk has become chief after his fathers death. The tribe lives as the old American Indians of old in the deserts of Arizona. The Kalkars have been driven to their last stronghold in the ruins of Los Angeles.
Red Hawk decides to lead his people once and for all to drive the Kalkars into the sea. Taking the whole tribe they go to California. There he is captured by the Kalkars but escapes. His adventures united him with a woman that is the descendant of Orthis. They encounter strange peoples and eventually drive the Kalkars into the sea. Red Hawk marries the descendant of Orthis ending the centuries feud.
The next two stories in the Moon series really takes it in a completely different direction. The story was originally envisioned as a Soviet takeover and titled Under the Red Flag.He was apparently several decades ahead of his time. He changed it to communist like Kalkars from the Moon. This is a different story that tackles themes as communism, pacifism, patriotism. The themes are still relevant today. Plus it is also a very good story with plenty of adventure and romance.