The term Sturmabteilung predates the founding of the Nazi Party in 1919. Originally it was applied to the specialized assault troops of Imperial Germany in World War I who used Hutier infiltration tactics. Instead of large mass assaults, the Sturmabteilung were organised into small squads of a few soldiers each. The first official German Stormtrooper unit was authorized on 2 March 1915. The German high command ordered the VIII Corps to form a detachment to test experimental weapons and develop tactics that could break the deadlock on the Western Front. On 2 October 1916, Generalquartiermeister Erich Ludendorff ordered all German armies in the west to form a battalion of stormtroops. They were first used during the 8th Army's siege of Riga, and again at the Battle of Caporetto. Wider use followed on the Western Front in the Spring Offensive in March 1918, where Allied lines were successfully pushed back tens of kilometers.
The DAP (Deutsche Arbeiterpartei, German Workers' Party) was formed in Munich in January 1919 and Adolf Hitler joined it in September of that year. His talents for speaking, publicity and propaganda were quickly recognized, and by early 1920 he had gained authority in the party, which changed its name to the NSDAP (Nationalsozialistische Deutsche Arbeiterpartei or National Socialist German Workers' Party) in February 1920, although "Socialist" was added by the party's executive committee, over Hitler's objections, to help the party appeal to left-wing workers.
The precursor to the Sturmabteilung had acted informally and on an ad hoc basis for some time before this. Hitler, with an eye always to helping the party to grow through propaganda, convinced the leadership committee to invest in an advertisement in the Münchener Beobachter (later renamed the Völkischer Beobachter) for a mass meeting in the Hofbräuhaus, to be held on 16 October 1919. Some 70 people attended, and a second such meeting was advertised for 13 November in the Eberl-Bräu beer hall. About 130 people attended; there were hecklers, but Hitler's military friends promptly ejected them by force, and the agitators "flew down the stairs with gashed heads". The next year, on 24 February, he announced the party's Twenty-Five Point program at a mass meeting of some 2,000 people at the Hofbräuhaus. Protesters tried to shout Hitler down, but his former army companions, armed with rubber truncheons, ejected the dissenters. The basis for the SA had been formed.
A permanent group of party members who would serve as the Saalschutzabteilung (meeting hall protection detachment) for the DAP gathered around Emil Maurice after the February 1920 incident at the Hofbräuhaus. There was little organization or structure to this group. The group was also called the Ordnertruppen around this time. More than a year later, on 3 August 1921, Hitler redefined the group as the "Gymnastic and Sports Division" of the party (Turn- und Sportabteilung), perhaps to avoid trouble with the government. It was by now well recognized as an appropriate, even necessary, function or organ of the party. The future SA developed by organizing and formalizing the groups of ex-soldiers and beer hall brawlers who were to protect gatherings of the Nazi Party from disruptions from Social Democrats (SPD) and Communists (KPD) and to disrupt meetings of the other political parties. By September 1921 the name Sturmabteilung (SA) was being used informally for the group. Hitler was the official head of the Nazi Party by this time.
The Nazi Party held a large public meeting in the Munich Hofbräuhaus on 4 November 1921, which also attracted many Communists and other enemies of the Nazis. After Hitler had spoken for some time, the meeting erupted into a mêlée in which a small company of SA thrashed the opposition. The Nazis called this event the Saalschlacht ("meeting hall battle"), and it assumed legendary proportions in SA lore with the passage of time. Thereafter, the group was officially known as the Sturmabteilung.
The leadership of the SA passed from Maurice to the young Hans Ulrich Klintzsch in this period. He had been a naval officer and a member of the Erhardy Brigade of Kapp Putsch fame, and was, at the time of his assumption of SA command, a member of the notorious Organisation Consul (OC). The Nazis under Hitler were taking advantage of the more professional management techniques of the military.
In 1922, the Nazi Party created a youth section, the Jugendbund, for young men between the ages of 14 and 18 years. Its successor, the Hitler Youth (Hitlerjugend or HJ), remained under SA command until May 1932. Hermann Göring joined the Nazi Party in 1922 after hearing a speech by Hitler. He was given command of the SA as the Oberster SA-Führer in 1923. He was later appointed an SA-Gruppenführer (lieutenant general) and held this rank on the SA rolls until 1945.
From April 1924 until late February 1925 the SA was reorganized into a front organization known as the Frontbann to circumvent Bavaria's ban on the Nazi Party and its organs (instituted after the abortive Beer Hall putsch of November 1923). While Hitler was in prison, Ernst Röhm helped to create the Frontbann as a legal alternative to the then-outlawed SA. In April 1924, Röhm had also been given authority by Hitler to rebuild the SA in any way he saw fit. When in April 1925 Hitler and Ludendorff disapproved of the proposals under which Röhm was prepared to integrate the 30,000-strong Frontbann into the SA, Röhm resigned from all political movements and military brigades on 1 May 1925. He felt great contempt for the "legalistic" path the party leaders wanted to follow and sought seclusion from public life. Members of the SA were, throughout the 1920s and into the 1930s, often involved in street fights called Zusammenstöße (collisions) with members of the Communist Party (KPD). In 1929, the SA added a Motor Corps for better mobility and a faster mustering of units.
In September 1930, as a consequence of the Stennes Revolt in Berlin, Hitler assumed supreme command of the SA as its new Oberster SA-Führer. He sent a personal request to Röhm, asking him to return to serve as the SA's chief of staff. Röhm accepted this offer and began his new assignment on 5 January 1931. He brought radical new ideas to the SA, and appointed several close friends to its senior leadership. Previously, the SA formations were subordinate to the Nazi Party leadership of each Gau. Röhm established new Gruppen which had no regional Nazi Party oversight. Each Gruppe extended over several regions and was commanded by a SA Gruppenführer who answered only to Röhm or Hitler. Under Röhm as its popular leader and Stabschef (Staff Chief), the SA grew in importance within the Nazi power structure, growing to thousands of members. In the early 1930s, the Nazis expanded from an extremist fringe group to the largest political party in Germany, and the SA expanded with it. By January 1932, the SA numbered approximately 400,000 men.
Many of these stormtroopers believed in the socialist promise of National Socialism and expected the Nazi regime to take more radical economic action, such as breaking up the vast landed estates of the aristocracy once they obtained national power. By the time Hitler assumed power in January 1933, SA membership had increased to approximately 2,000,000—twenty times larger than the Reichswehr (German Army).