Operation Himmler (less often known as Operation Konserve or Operation Canned Goods) was a 1939 false flag project planned by Nazi Germany to create the appearance of Polish aggression against Germany, which was subsequently used by Nazi propaganda to justify the invasion of Poland. This included staging false attacks on themselves using innocent people or concentration camp prisoners. Operation Himmler was arguably the first act of the Second World War in Europe.
For months prior to the 1939 invasion, German newspapers and politicians like Adolf Hitler had carried out a national and international propaganda campaign accusing Polish authorities of organizing or tolerating violent ethnic cleansing of ethnic Germans living in Poland.
The plan, named after its originator, Heinrich Himmler, was supervised by Reinhard Heydrich and managed by Heinrich Müller. The goal of this false flag project was to create the appearance of Polish aggression against Germany, which could be used to justify the German invasion of Poland. Hitler also might have hoped to confuse Poland's allies, the United Kingdom and France, into delaying or stopping their declaration of war on Germany.
The operations were mostly carried out on 31 August 1939. The operation - as well as the main German offensive - was originally scheduled for 26 August; the shifting diplomatic situation resulted in delay until 31 August/1 September - but one of the German undercover units was not informed and carried out its attack on a German customs post; several Germans were killed before the incident ended. The operations were carried by agents of the SS and the SD. The German troops, dressed in Polish uniforms, would storm various border buildings, scare the locals with inaccurate shots, carry out acts of vandalism, and retreat, leaving behind dead bodies in Polish uniforms. The bodies were in fact prisoners from concentration camps; they were dressed in Polish uniforms, killed (by a lethal injection, then shot for appearance) and left behind. They were described in plans as "Konserve", i.e. 'canned goods' (which also led to the more informal name of the operation, Operation Konserve).