The Sturmabteilung (SA)
Background
The Sturmabteilung (SA) literally measn Storm Detatchment. They were commonly known as Brownshirts or Stormtroopers. The nickname brownshirts was derived from their uniform color, these uniforms were cheap to buy after World War One due to an abundant supply. They opposed the Versailles Treaty, the weakness of the Weimar Republic, and even fought the Bavarian Soviets. Their mottos were: "Terror must be broken by terror." and "All opposition must be stamped into the ground."

Purpose
The SA was the original paramilitary wing of the Nazi party. Its primary purpose was to protect the Nazi rallies and assemblies from the other political paramilitary groups. Another purpose of the SA was to go out and disrupt political rivals assemlies and rallies, most often the German Communist Party (KDP) and the Social Democrats (SDP). These clashes netween the parties often resulted in street battles which were known as Zusammenstobe (Collisions). A secondary mission of the SA was to intimidate the Slovaks, Romani, Uniformists, Jews, and anyone else who opposed the Nazi Party.

Origination
The term SA originates back to World War One. It was used for Germans who used stealth tactics to cause a disruption behind enemy lines. The actual origination of the SA came from the Freikorps. The Freikorps were paramilitary groups to bolster the actual military. They were formed by individuals who were usually former German military officers. Munich in 1919 there was a Communist uprising started by the Bolshevik Bavarian Soviet Republic, the Freikorps came in and crushed the rebellion. This resulted in two things: 1. The Freikorps were deemed as a just organization, 2. It began anti-Communist feelings in Germany. Many people from the Freikorps would eventually join the SA.
During Hitler's rise to power he used his military friends to remove disrupters from meetings. The SA was a great asset to Hitler in his political rise to Chancellor. When violence broke out in the Weimar, the police appeared powerless to stop it. The order would then be restored by the SA.

History
The first leader of the SA before it was officially founded was Emil Maurice (1920-1921), the top leader was known as the Oberster SA-Fuhrer (Supreme SA leader). On November 4, 1921 the SA came into being after the brawl in the Hofbrauhaus, most of the members were ex-soldiers and young men aspiring to find some excitement. Leadership of the SA was turned over to Ulrich Klintzsch, who was a naval officer. During the early years of the SA the uniforms that they wore were not their iconic brown but they were instead an old custom's official uniform.
In 1922 the SA created the Jugenbund, which was a teen organization for boys only from the ages of 14-18. In 1923 the SA falls into disarray after the failed Beer Hall Putsch and they went undercover. From April 1924 to February 1925 they reassembled under the codename of the Frontbann. In 1925 the SA reorganizes publicly and resumes its previous roles. It also engages in voter intimidation in national and local elections. On April 4th the SS (Schutzstaffel) was formed as a branch of the SA.
In 1931 the SA reached a high of 100,000 members. In January Ernst Rohm became a popular leader of the SA. Ernst Rohm was an anti-capitalist who wished to see the Weinmar toppled and the SA to replace it. Ernst Rohm restructured the SA. His desire was for the SA to introduce a revolution to bring socialism into the country. Ernst Rohm creates the General Staff and Training College in Munich to give his men proper training. Hitler orders Rohm to take "Possession of the streets" as they held "the key to the power of the state."
In 1932 the SA reaches 400,000 members. Due to their intimidation tactics President Hindenburg orders the SA off of the streets for the elections. As an example of their violence the SA participated in 400 street battles that resulted in 82 deaths. Also in 1932, the Jugenbund renamed the Hitler Youth separates from the SA to become its own entity.
In 1933 the SA reaches 2 million members. On January 30 the SS separates from the SA. After the Nazi's take power the SA was largely riotous in the streets. Even foreign diplomats were complaining of being manhandled.
In 1934 they reached a 2.9 million in August and 3 million by the end of the year. During the Nazi Nuremberg Rally the SA was strongly featured and their soon to be leader was heavily covered. The SS even though a separate entity was restructured by Himmler and Heidrich and officially declared independent of the SA. On April 20th the Gestapo (Prussian secret police) is transferred to the SS by Goring. From June 30 to July 2 the SA is targeted along with other troublesome leaders of different organizations that were considered a threat to the Nazi's.
In 1935 Victor Lutze was placed in charge of the SA. He downsized the SA and prioritized the Jews as the main target. The SA was reorganized: Men from 18-35 were sent to active duty, Men 35-45 were sent to reserves to keep public order, and Men 45 and over were assigned to local militias.
By April of 1938 the SA membership was only 1.2million members. In November they initiated Kristallnacht (Crystal Night): the SA started riots against Jews. This resulted in 7000 storefronts vandalized, 29 department stores vandalized, a total of 7500 businesses were vandalized, 200 synagogues were damaged or destroyed, some Jews were beaten to death, and 30,000 men were sent to concentration camps.
In 1939 The SA became the training grounds for the Home Guard. By the time World War Two started the SA held little influence in the Nazi party as it was overshadowed by the SS. The SA however was not completely taken out of service until the end of the war. It is interesting to note that at the end of the war the Nuremberg Military Tribunal dismissed the SA from warcrimes and called the group as nothing more than "ruffians" and "bullies."

Leaders
The head of the SA was known as the Oberster SA-Fuhrer (Supreme SA leader)
Emil Maurice (1920-1921)
Hans Ulrich Klintzsche (1921-1923)
Herman Goring (1923)
None (1923-1925)
Franze Pfeffer von Salomon (1926-1930)
Adolf Hitler (1930-1945)

Hitler quelled the Stenned Revolt in 1930. After the revolt he took personal charge of the SA and made all of the members to swear loyalty to him.
The day to day operations of the SA then fell to the Stabschef-SA (SA Chief of Staff)
Oho Wagener (1929-1931)
Ernst Rohm (1931-1934)
Victor Lutze (1934-1943)