Nacht der langen Messer (the Night of the Long Knives) officially called by its perpetrators Unternehmen Kolibri (Operation Hummingbird) was a series of political extrajudicial (i.e. illegal) executions ordered by Adolf Hitler and carried out by the SS (paramilitary organization within NSDAP), Gestapo (political police of the German state) and Göring’s personal police battalion (ditto) from June 30 to July 2, 1934. For all practical purposes, it was a totally and completely illegal mass murder.
The Night of the Long Knives is often referred to as “the Röhm Purge” or “the SA Purge”. Which is not exactly correct as Ernst Röhm and other SA leaders murdered during Unternehmen Kolibri were not the only victims of this massacre.
In addition to their SA rivals, the SS and Gestapo (by that time already controlled by the SS) murdered leading members of the left-leaning “Strasser faction” of the Nazi Party, including its figurehead, Gregor Strasser, and several prominent conservatives and anti-Nazis, such as former Chancellor Kurt von Schleicher and Bavarian politician Gustav Ritter von Kahr (who had suppressed Hitler’s Munich Beer Hall Putsch in 1923).
In addition, more than 1,000 individuals deemed by the Nazis to be a threat to their regime, were arrested and sent to concentration camps without trial (which was legal due to the infamous Reichstag Fire Decree).
Hence the legal definition of this crime was twofold: (mass) murder and conspiracy to commit murder. A substantial number of individuals who did not actually commit murders could have been charged with either felony murder (being present at the time and place of the murder) or at least accessory to murder.
Actions committed by the abovementioned perpetrators were illegal (i.e. criminal) according to German law in effect at that time because even if Röhm and other SA leaders planned a coup (and they did not) against Adolf Hitler and Nazi government (both legit at the time), there still was a legal due process to be followed to deal with them.
Nazis did not follow this due process and executed their victims without trial thus committing a crime. And a capital crime at that.
Concerned with presenting the massacre as legally sanctioned, Hitler had his cabinet approve a measure on July 3 that declared:
“The measures taken on June 30, July 1 and 2 to suppress treasonous assaults are legal as acts of self-defense by the State.”
Reich Justice Minister Franz Gürtner, a conservative who had been Bavarian Justice Minister in the years of the Weimar Republic, demonstrated his loyalty to the new regime by drafting the statute, which on the surface added a legal veneer to the purge.
Signed into law by Hitler, Gürtner, and Minister of the Interior Wilhelm Frick, the “Law Regarding Measures of State Self-Defense” retroactively legalized the murders committed during the purge. Which was illegal – plain and simple as laws (especially those that legalize mass murder) can not be applied retroactively.
And even if they could as there were no “treasonous assaults” (even planned, let alone committed), the whole Operation Hummingbird was totally and completely illegal (i.e. was a heinous crime).
Officially, the Nazis admitted to murdering 83 individuals – the SA leaders and Hitler’s actual, potential or perceived political opponents (or just “political undesirables” which included several Jews).
The unofficial estimates run from 89 to a whopping 1,000. However, most historians agree that the total number of victims does not exceed a hundred. For comparison – during the Great Purge of 1937-38 Stalin’s mass murdered killed ten times that every day.