a small restaurant. He befriends a young woman, Isobel, when he tries to send a message to his parents. However, communication with Mars has been cut due to the hostilities. Harvey settles in to wait out the war, but the war comes to him. Earth sends a force to put down the rebellion on Venus. The Venerian ships are destroyed in orbit and the ground forces are routed. Charlie is killed resisting the occupying soldiers. Harvey is rounded up and questioned by a senior security officer, who is very eager to get his hands on Harvey's ring. Luckily, Harvey had given it to Isobel for safekeeping; he does not know where she is or whether she is even alive. Before he can be interrogated with drugs, he escapes and joins the Venerian guerrilla forces. Harvey joins the army of the Republic and becomes an effective commando. In time, he is tracked down by the leaders of the resistance, who are also looking for the ring. Isobel and her father (an important member of the rebels) are safe at the very base where Harvey is taken. The seemingly valueless ring turns out to contain the secret of scientific breakthroughs resulting from archaeological studies of an extinct alien civilization on Mars. With Sir Isaac's assistance, the rebels use the information to build an advanced spaceship that is much faster than any other vessel in existence, with revolutionary weapons and defenses also derived from the new technology. As a combat veteran, Harvey is recruited for the maiden voyage of Little David, manning a dead man's switch, with strict orders to blow up the ship if it is in danger of capture. Little David intercepts and defeats a task force of warships on their way to Mars to crush the revolt there. Astronomy Like many science fiction works of its period, the novel depicts both Venus and Mars as suitable for human habitation. Since no interplanetary space probes had been launched at the time, neither the extreme pressure and temperature at the surface of Venus, nor the extremely low atmospheric pressure at the surface of Mars, were known to science. Even the length of the day on Venus was not yet known. Reception Groff Conklin reviewed the novel favorably, calling it "a magnificently real and vivid Picture of the Possible". Boucher and McComas named it among the best sf novels of 1951, characterizing it