Krüger was born into a military family in Strasbourg, Germany (nowadays France) in 1894; he received elementary school education, but ultimately left school before graduating to begin a military career as a cadet in military schools in Karlsruhe and Grosslichterfelde.
In 1914, his father, Alfred Krüger, died; Krüger himself received a commission in June the same year, becoming a lieutenant when World War I broke out. During the course of the war, he was wounded three times and awarded, along with several lesser decorations, the 1st and 2nd class Iron Crosses.
Following the end of the war, Krüger first joined a naval brigade; in August 1919, he became a member of the Freikorps von Lützow, which he left again in March 1920. Returning to civil employments, he worked as a clerk in Berlin until 1923, then assumed another position as the director of a refuse company in 1924. He stayed in that position until 1928, then left the company after finding it corrupt, and instead began a career as a self-employed entrepreneur.
Krüger married in 1922; he had a total of two children with his wife and also adopted three foster children.
While working at the refuse company, he probably also met Kurt Daluege for the first time; Daluege, who was an engineer at the company at that time, would later on become SS commander in Berlin and leader of the Ordnungspolizei ("order police"), and the two men soon formed a friendship.
In November 1929, Krüger then entered the NSDAP as member #6123; in February 1931, he also joined the SS, which he left abruptly in April to transfer to the SA. With the help of Daluege, Krüger instantly acquired the SA rank and the power necessary to conduct reforms of the “SA Formation East”; he was promoted to SA-Gruppenführer (equivalent to major-general) in 1932 and joined Ernst Röhm's personal staff.
In June 1933, Krüger was promoted again to SA-Obergruppenführer (equivalent to Lieutenant general) and appointed chief of the Ausbildungswesen ("training", AW). Cooperating closely with the Reichswehr, he used his new position to school the SA's best recruits (an estimated 250,000) to become officers.
Krüger was not caught in the Night of the Long Knives, in which Röhm and many other high-ranking SA members were killed, and it has been speculated that his switch from the SS to the SA was only carried out due to pragmatic reasons, especially in the light of Krüger trasferring the SA armouries of which he was in charge to the Reichswehr as soon as the purge had begun. Nevertheless, Krüger was left without a job temporarily, until he entered the SS again, still keeping his SA rank as well.
In 1935, Krüger was appointed SS-Oberabschnittsführer; his career was discussed by the SS leadership and Adolf Hitler and, on February 21 1936, he was appointed inspector of border guard units as well as Hitler's personal representative at a variety of formal and informal NSDAP events.
Krüger continued to demonstrate his loyalty to Nazism, as well as his military, police and administration skills and was made Höherer SS- und Polizeiführer ("Higher SS and police leader, HSSPF), becoming one of Heinrich Himmler's representatives, although he lost the position again in November 1943 following disagreements between Himmler and Hans Frank. Half a year later, he wrote in a letter, "I have lost honour and reputation due to my four year struggle in the GG" ("Ich habe für meinen vierjährigen Kampf im GG Ehre und Reputation verloren."), and at the end of World War II, he followed Hitler, Himmler and Odilo Globocnik by committing suicide, shooting himself in Libau on May 9, 1945.