Born Smedley Darlington Butler on July 20, 1881, to Thomas Butler and Maud M. Darlington, Smedley Darlington Butler had a more military and government centered life than probably most children born to Quaker men. Butler's father was a state representative and no doubt influenced his decision to be actively involved with his country. Butler was educated at the Haverford School, and at the age of 16, he enlisted in the military, fabricating his birth date to make himself eligible. When his father confronted him about it, he asked, "How old did thee say thee was?" to which Butler told his father that he had told the Marine Corps that his birth date was April 20, 1880. His father replied, "If thee is determined to go, thee shall go, but don't add another year to your age, my son. Thy mother and I weren't married until 1879."

Butler was commissioned into the Marines as a second lieutenant. As such, he was not eligible for what could have been his first Medal of Honor. During the Boxer Rebellion in China in 1900, Butler and five other men carried a wounded officer 17 miles through heavy fire to the nearest medical station. Because of this, four of the men received Medals of Honor, but Butler and the other officer did not, because at that time the Medals could not be given to officers. However, his actions did warrant his being promoted to brevet captain.

His first Medal of Honor was a result of his bravery in Veracruz, Mexico, in 1914. His official citation read that he earned it for his being "eminent and conspicuous in command of his battalion. He exhibited courage and skill in leading his men through the action of the 22d and in the final occupation of the city." However, 56 Medals of Honor were handed out during that campaign, and many military personnel thought that diminished the prestige. Butler was one of those people. He tried to give his back, claiming he had not done anything worthy of the Medal. The military gave it back to him and he was commanded to wear it with pride on his uniform.

Butler's second Medal of Honor was undoubtedly well earned. During World War I, Haiti's unstable government left them susceptible to German influence. Then President Woodrow Wilson sent military forces there to protect the Americans living there and stabilize their government. During the Haitian campaign in 1915, Fort Riviere became one of the last strong-holds of the rebelling Haitians. Butler was determined to take the fort, and convinced his colonel that he could take it with four companies of 24 men each and two machine gun detachments, much less than was thought needed for the endeavor. After approaching the fort, the Marines realized the only way to it was through a drain that was four feet high. While a Haitian fired into the drain, Butler and two other men climbed through it, dodging bullets the whole time. All three made it through, and the companies of men took the fort. Butler and the two other men were awarded the Medal of Honor for their bravery in taking the fort.

After receiving the two Medals of Honor, Butler returned to the United States and commanded the Marine training base in Quantico, Virginia. After the Haitian Campaign, he then took a leave from the military from 1924 to 1925 to serve as Philadelphia's police commissioner, with the goal of enforcing Prohibition. Butler then went back into the military, serving in China until 1927 and becoming the youngest major general in the Marine Corps in 1929. Butler retired from the Marine Corps soon after that in 1931.

Butler was passionate about the military and, after his retirement, became an author and lecturer on the subject. No doubt his Quaker background colored his pacifist beliefs about the military, though he diligently served his country in a number of battles for many years. One of his most famous quotations seems to contradict what he did in service to his country. He said, "I spent thirty-three years and four months in the Marine Corps. During that period I spent most of my time being a high-class muscle man for Big Business, for Wall Street and for bankers. In short, I was a racketeer for capitalism. I helped make Mexico safe for American oil interests in 1914. I helped make Haiti and Cuba a decent place for the National City Bank boys to collect revenues. I helped purify Nicaraguans for the international banking house of Brown Brothers in 1909-1912. I brought light to the Dominican Republic for American sugar interests in 1916. I helped make Honduras 'right' for American fruit companies in 1903." Many people rejected Butler for his comments, but he went on to write a book dedicated to what he saw as a more important cause, exercising his right to free speech to speak out against what he saw as an oppressive government and military.

His book, War is a Racket, laid out what many saw as an isolationist plan for the United States military. He wanted to set physical boundaries for the military and limit its activity to at most 500 miles off the coasts. Butler also saw the great gap in wages among military personnel gravely unfair. He thought that the man in the trenches should be getting paid the same as the officers and official in the armed forces. His public persona as an isolationist was enhanced by his involvement with the League Against War and Fascism and the Third US Congress Against War and Fascism. Though not well liked among his colleagues in the government who agreed with the policies Butler spoke out against, he was well respected because of his unwavering convictions. The Pacifist Movement gained ground because of people like Smedley Butler and Gandhi. The Peace Congress and the Pacifist Resolution of the Students' Union at Oxford also helped progress the movement.

In 1933, plotters to overthrow the government tried to play on Butler's convictions. They asked him to lead a company of 500,000 men on a march in Washington, D.C., for the gold standard that would ensure retiring soldiers were taken care of by the government. Butler saw through their rhetoric to their plot to take over the government, however, and turned them in to the authorities. These steadfast beliefs and his good character is what earned him the respect of his superiors and those below him as well. One of his men said, "I'd cross hell on a slat if Butler gave the word." Butler also ran for the Senate in the primaries as a Republican in 1932, but he was defeated by Republican incumbent James J. Davis.

During his lifetime, Butler had accomplishments aside from the military and his own initiatives to speak out against the government. In 1926, he was a military consultant for the movie Tell it to the Marines. The silent film was about a young, somewhat unserious Marine who was put in line by a more rigid superior. Because Butler was stationed in San Diego, California, at the time and had a reputation of being a tough soldier, he was asked to be a consultant for the movie. Also, footage of him has been used in three other movies: Endgame: Blueprint for Global Enslavement, released in 2007; The Corporation, released in 2003; and The Great Depression, released in 1993. Butler died of cancer in 1940 in Philadelphia, and is buried in West Chester, Pennsylvania.