June 30, 1934 was the Night of the Long Knives, Hitler's purge of those standing in his way

Herr Adolf Hitler, the German Chancellor, has saved his country. Swiftly and with exorable severity, he has delivered Germany from men who had become a danger to the unity of the German people and to the order of the state. With lightening rapidity he has caused them to be removed from high office, to be arrested, and put to death.

The names of the men who have been shot by his orders are already known. Hitler's love of Germany has triumphed over private friendships and fidelity to comrades who had stood shoulder to shoulder with him in the fight for Germany's future.

~Daily Mail, July 2nd 1934.

Hitler posing with SA members in the late 1920s. 

Hermann Göring stands bedecked 

with medals beneath Hitler.

The Night of the Long Knives (wiki)(sometimes called Operation Hummingbird or, in Germany, the Röhm-Putsch), was a purge that took place in Nazi Germany from June 30 to July 2, 1934, when the Nazi regime carried out a series of political murders.

When Hitler rose to power in early 1933, he owed much of his success to the muscle of his Nazi Storm Troopers, the SA (Sturmabteilung), a violent, ruthless army headed by Ernst Röhm, Hitler’s long-time friend and devotee. Röhm and his Storm Troopers brought Germany into submission by gaining control of the streets gangster-style and violently eliminating any of Hitler’s political enemies.

By the summer of 1934, the SA's numbers had swollen to 2 million men. The SA had given the Nazis an iron fist with which to disrupt other political parties' meetings before Hitler became Chancellor in January 1933, and was also used to enforce law afterwards: essentially, they were the enforcers of the Nazi Party.

Hitler and Rohm, 1933

However, a threatening, revolutionary force such as the SA was no longer useful now that Hitler was firmly in power. Hitler wanted to “go legit” and win over the regular army generals, the leaders of industry, as well as the German people. Most everyone in Germany disliked the SA, who were seen as the arrogant, bullying, murderous thugs that they were, and Hitler knew he needed to curtail their power to increase and solidify his own.

Hitler knew that the army hierarchy held him in disdain as he was 'only ' a corporal in their eyes, and the regular army hierarchy also saw the SA as a threat to their authority. The SA outnumbered the army by 1934 and Röhm had openly spoken about taking over the regular army by absorbing it into the SA. Such talk alarmed the army's leaders, and in April of that year, Hitler and the head of the German army, Werner von Blomberg, signed a secret agreement in which Hitler promised Blomberg’s army absolute control of the military (with precedence over the SA); and von Blomberg pledged the army’s backing when Germany’s 86-year-old president Paul von Hindenburg inevitably shuffled off the mortal coil and Hitler claimed the presidency.

Ernst Rohm

Röhm had made powerful enemies in the Nazi party, among them Heinrich Himmler and Hermann Goering, who were part of the SS (Shutzstaffel), an organization that acted as Hitler’s personal body guards. They began putting the bug in Hitler’s ear that Röhm was planning a coup, and even gathered false evidence to back up their bogus claim - there is no actual evidence that Röhm was ever planning anything against Hitler.

When Hitler met with German President Paul von Hindenburg on June 21, 1934, the old man was in very poor health and was confined to a wheelchair, but his mind was sharp as ever. He brusquely informed Hitler and Defense Minister Blomberg that the SA must be brought to heel ASAP, or he would declare martial law in Germany and let the army run the show, which would pretty much mean the end of the Nazi party.

On the evening of June 30, 1934, which became known as the Night of the Long Knives (wiki), Hitler made his move. In the village of Bad Wiesse, the SS raided a hotel where Röhm and his buddies were hanging out for the weekend. Members of the SA were dragged from their beds and executed on the spot.

Just before Wiessee, Hitler suddenly breaks his silence: "Kempka", he says, "drive carefully when we come to the Hotel Hanselbauer. You must drive up without making any noise. If you see a SA guard in front of the hotel, don't wait for them to report to me; drive on and stop at the hotel entrance." Then after a moment of deathly silence: "Röhm wants to carry out a coup." An icy shiver ran down my back. I could have believed anything, but not a coup by Röhm.

~Kempka, I Was Hitler's Chauffeur

Units of the SS arrested more of the leaders of the SA and other political opponents. Seventy-seven men were executed on charges of treason though historians tend to think the figure is higher. Hitler also took the opportunity to assassinate anyone that he didn’t like, or had crossed him, or looked at him the wrong way.

Röhm was arrested by Hitler himself, brought to Munich, and given a revolver to kill himself instead of being executed by someone else. Röhm refused, saying if Adolf wanted him dead so badly, he’d have to do the deed himself. Since Hitler couldn’t bring himself to kill his old friend, he sent in a minion to shoot Röhm in the stomach at point-blank range. 

The SA was brought to heel and placed under the command of the army. The Night of the Long Knives not only removed the SA leaders but also got Hitler the army's oath that he so needed.

The first the public officially knew about the event was on July 13th 1934, when Hitler told the Reichstag that met in the Kroll Opera House, Berlin, that for the duration of the arrests that he and he alone was the judge in Germany and that the SS carried out his orders. 

“If anyone reproaches me and asks why I did not resort to the regular courts of justice, then all I can say is this: In this hour I was responsible for the fate of the German people, and thereby I became the supreme judge of the German people.” 

~Adolf Hitler, July 13, 1934

From that time on the SS became a feared force in Nazi Germany, lead by Heinrich Himmler. The efficiency with which the SS had carried out its orders greatly impressed Hitler and Himmler went on to acquire huge power within Nazi Germany.

Here's a brief Khan Academy video describing the event:

Watch the rest of Khan Academy's Rise Of Hitler and the Nazis here.

History channel 4 minute video, part of a longer documentary below:

Here's the 45 minute version of the History Channel video:

Got more time and interest?  Here's a 45 minute UKTV documentary:

Based on a post at the excellent Today I Found Out (their Wise Book of Whys went to several family members as Christmas presents last year), with input from here, here, and here.

Previous posts:

Nazis with cats.

Hitler’s Last Surviving Food Taster

Nazi sex dolls, intended to protect soldiers from French prostitutes.

Further reading: 

The definitive source: Rise And Fall Of The Third Reich.

Stormtroop Tactics: Innovation in the German Army, 1914-1918