The Sturmabteilung (SA, German for 'Assault Division' and sometimes translated stormtroopers) functioned as a paramilitary organisation of the NSDAP - the German Nazi party. It played a key role in Adolf Hitler's rise to power in the 1930s. SA men were often known as brown shirts from the color of their uniform and to distinguish them from the SS who were known as black shirts.
The term Sturmabteilung originally came from the specialized assault troops used by Germany in the March 1918 campaign in World War I. Instead of a large mass assault, the Sturmabteilung were organized into small teams of a few soldiers each. This allowed the Germans to push back British and French lines tens of kilometers.
Hitler himself founded the SA in 1921 in Munich. It originally functioned as a group of bodyguards to enforce order at Nazi gatherings. Under their popular leader, Ernst Röhm, the SA grew in importance within the Nazi power structure, eventually claiming thousands of members. The SA carried out numerous acts of violence against socialist groups throughout the 1920s, typically in minor street-fights. The SS eventually took over their original role.
After Hitler took power in 1933 the SA became increasingly anxious for power and saw themselves as the replacement for the German army. This angered the regular army (Reichswehr) who were already quite annoyed at the Nazi party. It also led to tension with other leaders within the party, who saw Röhm's increasingly powerful SA as a threat to their own personal ambitions.
In order to ally himself with conservative forces within the German Army and to strengthen his position within the Nazi Party, Hitler ordered the execution of the leadership of the SA which took place on 29 - 30 June, 1934 on what is known as the Night of the Long Knives. Victor Lutze became the new leader of the SA, and the organization was soon marginalized in the Nazi power structure.