In the summer of 1932 the re-election campaign of President Herbert Hoover was battling hard against the popularity of Franklin Delano Roosevelt who was promising to bring in programs to relieve the sufferings of the economic collapse they called the Slump or the Great Depression. At this worst imaginable time thousands of US veterans with their starving families, the "Bonus Army", invaded Washington demanding that Congress authorize payment of the war service bonus money the vets had been promised before the Crash of 1929.
The protesters set up camp across the Anacostia River. When Congress refused to grant the bonus the vets rioted. Clashes with the police resulted in two rioters being shot to death by overwhelmed police at the Armoury.
General Douglas MacArthur was ready with cavalry under George Patton and six tanks supported by bayonet armed troops. Hoover ordered MacArthur to clear the rioters from the area of DC proper but he explicitly forbade MacArthur from crossing the 11th Street Bridge into the Bonus camp with its crowds of women and children. MacArthur deliberately balled up and threw away the memo reiterating that order and charged over the 11th Street Bridge into the camp. At least one woman was bayonetted; casualties flooded the hospitals.
The news spread like a firestorm. Roosevelt was elected by a landslide.
In 1933 an attempt was made to shoot Roosevelt in Florida before his inauguration in March. After his inauguration a plot was hatched to stage an armed coup d'état to depose Roosevelt, suspend Congress and the Constitution and set up a fascist military dictatorship.
The principle plotters were the men who also were financing Hitler and arming his SA "Storm Troopers": the DuPont brothers Renee and Lamot; John Rockefeller Sr and John Jr; Henry and Edsel Ford.
The conspirators had thousands of trained men ready to go.
They would have asked MacArthur to lead them but he had lost popularity among the veterans, to put it mildly. They asked retired Marine Corps General Smedley Darlington Butler to be their American Hitler. Big mistake! Butler was a patriot.
Butler played along till he could gather evidence and then blew the whistle before the closed-door McCormack-Dickstein Congressional Committee. The plot was exposed and aborted. The Committee publicly affirmed the truth of Butler's accusations.
The men who would have destroyed the Republic had realized they couldn't depend on the US armed forces. They set to work developing their own private army. Wild Bill Donavan honchoed the development of the OSS as a spy and guerrilla and propaganda force to operate behind the lines in Europe.
After the War this force continued and in 1947 it became legitimized as the CIA. The private army was all ready and set up to be funded by the same Congressional chumps the CIA was eager to squash. So exactly 30 years after the first attempt to remove a president by violence had failed, success was achieved in Dallas on November 22, 1963. It went so smoothly the major part of the USA didn't even know they'd been relieved of their constitutional republic; they swallowed the whole "lone nut gunman" routine like the suckers they are.
The War in Vietnam was a huge business success. The continued democracy with its dumb annoying election campaigns was a pain in the rear though. They'd have to do something about that sooner or later.