Times were tense between the U.S. and Russia during the Cold War, but things never escalated into full-scale war.
If they had, newly declassified papers say the U.S. was ready to systematically destruct highly-populated areas, with Moscow and Leningrad atop the list.
The Strategic Air Command Atomic Weapons Requirements Study for 1959, uncovered and published by the National Security Archive, provides the most comprehensive and detailed list of the U.S.' Cold War plans to date.
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Declassified Cold War papers reveal where US was ready to attack
Trinity was the code name of the first detonation of a nuclear device, conducted by the United States Army on July 16, 1945 as a result of the Manhattan Project, in the Jornada del Muerto desert, New Mexico, at the new White Sands Proving Ground. Trinity used an implosion-design plutonium device, informally nicknamed 'The Gadget'.. (Photo by Universal History Archive/UIG via Getty Images)
A photograph on display at The Bradbury Science Museum shows a hydrogen bomb test on June 24, 1957. The museum is Los Alamos National Laboratory's window to the public. The Museum displays the Laboratory's current research and presents the history of the Laboratory's role in the Manhattan Project during World War II. (photo by Joe Raedle)
A photograph on display at The Bradbury Science Museum shows the first thermonuclear test on October 31, 1952. The museum is Los Alamos National Laboratory's window to the public. The Museum displays the Laboratory's current research and presents the history of the Laboratory's role in the Manhattan Project during World War II. (photograph on display in the Bradbury Science museum, photo copied by Joe Raedle)
Trinity was the code name of the first detonation of a nuclear weapon, conducted by the United States Army as part of the Manhattan Project. 16th July 1945. Device type: Plutonium implosion fission. Yield: 20 kilotons of TNT. The White Sands Proving Ground, where the test was conducted, was in the Jornada del Muerto desert about 35 miles (56 km) southeast of Socorro, New Mexico, on the Alamogordo Bombing and Gunnery Range. New Mexico, USA. (PHoto by Galerie Bilderwelt/Getty Images)
Aerial view of the massive K-25 gaseous diffusion plant, Oak Ridge, Tennessee, early August, 1945. The plant and, indeed, the entire city of Oak Ridge, was established in 1942 to house the employees (and their families) of the uranium-enrichment facility of the Manhattan Project, the United State's project to develop the atomic bomb. (Photo by PhotoQuest/Getty Images)
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The papers say the U.S. had plans to target "population" cities, including Beijing, Moscow, Leningrad, East Berlin and Warsaw.
The National Security Archive writes, "Purposefully targeting civilian populations as such directly conflicted with the international norms of the day, which prohibited attacks on people per se (as opposed to military installations with civilians nearby)."
The U.S. supposedly wanted to focus on destroying Russia's air power, which appeared to be the biggest threat to the U.S. and its allies.
Moreso, the papers say the U.S. wanted to drop bombs "ranging from 1.7 to 9 megatons" on these air power targets. There were also plans to develop a 60-megaton weapon.
As the National Security Archive explains, "One megaton would be 70 times the explosive yield of the bomb that destroyed Hiroshima."
The Cold War was a major test for President John F. Kennedy, who said in a presidential address, "The event of nuclear weapons changed the course of the world as well as the war. Since that time, all mankind has been struggling to escape from the darkening prospect of mass destruction on earth."
See more of Kennedy through his life:
John F Kennedy (life)
Declassified Cold War papers reveal where US was ready to attack
1927: Headshot portrait of John F Kennedy (1917-1963) at age ten, standing outdoors and wearing a suit with his hair slicked back. (Photo by Hulton Archive/Getty Images)
Future President of the United States of America, John F Kennedy (1917 - 1963) in London. (Photo by Evening Standard/Getty Images)
American statesman John F Kennedy, later the 35th President of the United States (right), with Mr Borhum at a garden party at the White House, Washington DC. (Photo by Fox Photos/Getty Images)
1st September 1939: Joe, Kathleen and John F Kennedy, the children of American Ambassador to Great Britain, Joseph P Kennedy, arriving at the Houses of Parliament in London. John later became the 35th President of the United States. (Photo by Fox Photos/Getty Images)
A photo dated 1950's shows John F. Kennedy with his wife Jacqueline Bouvier Kennedy. (Photo credit should read AFP/AFP/Getty Images)
John Fitzgerald Kennedy (1917 - 1963), the American president sitting in a rocking chair. (Photo by Keystone/Getty Images)
Senator John F Kennedy seeking the Democratic nomination for the presidential elections, which he went on to win. (Photo by Keystone/Getty Images)
President John F. Kennedy speaks on the telephone August 23, 1962 in the Oval Office. (Photo by National Archive/Newsmakers)
Senator John F Kennedy (1917 - 1963) is given a rousing ovation during his presidential campaign. (Photo by Keystone/Getty Images)
John F Kennedy (1917 - 1963), American president-elect, with his wife Jacqueline (1929 - 1994) at the christening of their son John F Jr. (1960 - 1999) in Washington. (Photo by Keystone/Getty Images)
U.S. President John F. Kennedy (1917 - 1963) holds his first press conference, Washington D.C., 28th January 1961. (Photo by Central Press/Hulton Archive/Getty Images)
17th February 1961: Jacqueline Kennedy (1929 - 1994), wife of US President John F Kennedy, and daughter Caroline relax together at home. (Photo by Keystone/Getty Images)
1962: US statesman John F Kennedy, 35th president of the USA, making a speech. (Photo by Central Press/Getty Images)
US President John F Kennedy (1917 - 1963, left) with British Prime Minister Harold Macmillan (1894 - 1986) outside Government House in Hamilton, Bermuda, where they are holding talks, 22nd December 1961. (Photo by AFP/Getty Images)
President John F. Kennedy greets wellwishers after a speech May 8, 1963 at the White House. (Photo by National Archive/Newsmakers)
9th November 1960: Senator John F Kennedy, the Democratic candidate who has been elected president of the USA. (Photo by Keystone/Getty Images)