See study by N. Valis, The Decadent Vision in Leopoldo Alas (1981).
Standing afar off for the fear of her torment, saying, Alas, alas that great city Babylon, that mighty city! For in one hour is thy judgment come.
Randy Bragg, the protagonist, is a man who dabbles at law and lives a life with little purpose. A former Korean War infantry officer, he ran for the state legislature and was soundly defeated because he supported the Supreme Court decision of Brown v. Board of Education; this forced his retirement from public life. This changes when his brother, Colonel Mark Bragg, sends him a telegram with the code words "Alas, Babylon"—their private code for disaster. Mark, who is on the Air Intelligence staff of the Strategic Air Command (SAC), is certain war between the United States and the Soviet Union is imminent. He sends his wife Helen and children Ben Franklin and Peyton to stay with Randy in Fort Repose, Florida.
Randy privately warns those people of Fort Repose whom he believes to be his friends; including Malachai Henry, his gardener.
A U.S. Navy fighter pilot, Ensign Cobb, callsign Peewee, fires a heat-seeking missile at a Soviet reconnaissance aircraft that same day. The missile goes off course and hits an ammunition depot at Latakia, Syria, resulting in an explosion that may include nuclear devices. This event is the pretext (called in the text a casus belli) for the Soviet Union to launch a pre-emptive nuclear strike against the United States.
Early the following morning, Mark is on duty at SAC headquarters at Offutt Air Force Base in Omaha, Nebraska. He suspects an attack is imminent. He recommends that SAC ask for the authority to use nuclear weapons since the weapons-release process takes about a minute and a half, and the U.S. expects only about a fifteen minute warning if the Soviet Union were to attack. This is granted. Later, when American radar reports an attack underway, the SAC commander says to him "Thanks for the ninety-five seconds."
In Fort Repose, Randy and his houseguests are awakened by shaking. "The Day" has begun. The effects of the war, called "The Day", on Fort Repose are varied. Tourists are trapped in their hotels. The local bank manager tries to get instructions from Jacksonville, but since Jacksonville is also home to several naval air stations and a homeport for naval warships, Jacksonville is destroyed. The local disc jockey nervously reads instructions on the CONELRAD system. The only reliable method of news from the outside world is a shortwave receiver owned by one of Randy's neighbors, a retired U.S. Navy admiral. Convicts break free of chain gangs; the local retirement homes are filled with panicked people; and the flash from a nuclear blast over the city of Tampa to destroy MacDill Air Force Base temporarily blinds Randy's niece, Peyton.
As the effects of the disintegration of society get worse, many prominent people fail. The local banker commits suicide once he realizes money is useless. Randy's political rival obtains looted radioactive jewelry and becomes seriously ill with radiation sickness. Randy, instead, grows stronger. He organizes his immediate neighbors to provide housing, food, and water for themselves, organizes the community into self-defense, guides his family, and helps find salt and new supplies of food when they grow short. He fights "highwaymen" who murder residents and assault the local doctor. Some in Fort Repose discover faith; others degenerate into drunkenness. Randy and his family fare the best, though, for when Randy needs something, he commandeers it. He is backed up legally by an order of President Josephine Vanbruuker-Brown (who was the Secretary of Health, Education and Welfare when "The Day" came) for any surviving active-duty or reserve officers to form local militias.
Also, his niece, Peyton, discovers an attic of antique wonders--a Victrola, old-fashioned straight razors, a treadle sewing machine--in his ancestral home, allowing the families to adapt more easily to life without electricity.
When the Air Force finally makes contact with Fort Repose again, the community has survived, but at a cost.
Alas, Babylon depicts fallout and radiation as an invisible threat, rather than a roaming "cloud of death" as in other novels such as On the Beach. Its theme is "You can survive if you are ready and willing to adapt."
The book also portrays nuclear war as arguably winnable. When the Air Force personnel find Randy and his survivors, they are asked about the outcome of the nuclear exchange and are told: "We won it. We really clobbered 'em!" (The value of this victory is questioned, even by the speaker, who adds, "Not that it matters"; he has already explained that the "victorious" United States now has a smaller population than pre-war France, and will be accepting lend-lease shipments of foodstuffs from South America, Thailand, and Indonesia.) The book presents the post-apocalyptic situation as grave but survivable, that even within the so-called "contamination zones", it is possible for some communities to continue. This book was written before the effects of Nuclear Winter and Electromagnetic pulses were widely known, but otherwise is reasonably accurate in the effects of a nuclear attack and its aftermath. The U.S. government is presented as functioning in uncontaminated areas, and working to help survivors as best as possible in contaminated zones. This depiction is very different from later books and films on nuclear war.
In the foreword of the 2005 edition of Alas, Babylon, David Brin admits that the book was instrumental in shaping his views on nuclear war and had an effect on his own book, The Postman (pp. xi-xii, ISBN 0-06-074187-2, Harper Perennial Modern Classics).
The television show Jericho is arguably a modern take on this tale.