Such events qare naturally overplayed by one side (Goebells certainly did) and completely dismissed by the other (As some Polish histories do). The Bromberg Massacre (300 is the low end 700 the high end) is sometimes explained in terms of Polish Officers shooting into the air to restore order, another is that these civilians (of a variety of documentate ages and genders) suddenly became non uniformed insurgents, another is that they carried Swastika arm bands (which would make them legal combatents incidently) or that they were mistaken for paratroopers without uniform.
All of these explanations I think would sound ludicrous to most folks.
http://www.deutsche-und-polen.de/_/them ... morde.html
Tidied up Machine translation:
"During the first days of the war, some thousands of ethnic Germans were killed by Poles in the chaos of the withdrawal as well as on the basis of nothing but suspicion. \the crimes later justified the anti-Polish measures of the German occupation power in Poland.
Murderous Assaults and Alibi for the Policies of Destruction
Immediately on the outbreak of the Second World War, "suspicious" ethnic Germans were interned and conveyed to the interior of the country. Many of them got caught up in the Polish retreat and perished, in part they were shot. In Bromberg and other localities with a German population, Germans were shot on the basis of extremely dubious accusations such as espionage, firing on Polish troops and suchlike,which for the most part rested on rumours and denunciations. In total, around 6,000 ethnic Germans died during the hostilieis between the Wehrmacht and the Polish Army. When members of the Polish armed forces and those killed for example by German bombing are deducted, there remain 4-5,000 Germans slain by Poles in the excitement of the first days of the war.
Soon after the investigation of the official numbers of victims, the dimension of the crime was multiplied tenfold in Hitler's command. The alleged 58,000 victims of the "September murders" and the "Bromberg bloody Sunday" served in the following period as justification for the systematically destructive occupation policies of Hitler Germany."
This is in the fairly politically correct language of modern Europe.
The disenfranchisment of Germans in Poland between the wars is documented by Alfred-Maurice de Zayas ; in "A terrible revenge" and "nemisis at Potsdam. These documents actually available in their thousands as ethnic Germans filed protests with the Legaue of nations.
I should point out that in the the 1930s in the Ukrainian part of Poland "Galacia" ethnic organisations were banned, and in 1930's the military and police carried out a number of pacification campaigns, which led to many arrests, widespread brutality and intimidation, and destruction of property. In 1930's Polish authorities promoted, sometimes by force, the conversion of the Orthodox to the Roman Catholicism (so-called Union) and seized hundreds of Orthodox churches for closure, destruction, or transfer to the Roman Catholic Church.
Polish nationalism was a very potent and agressive force in the 1930's and its many minorities had good reason to be in fear.
A summary of what really happened is given here on the tightly moderated axis history forum:
Axis History Forum • View topic - Polish brutality against ethnic German civillians in WW2
I would like to add that I have no problem with Poles or Poland, they deserve a place of their own and self determination and it is good to see them in new Europe. It is understandable that they were ardent. Poland was heir to the Polish Lithuanian Commonwealth and that entity was made of of many ethnicities who had been there for 1000-1500 years or more. Many of the Germans expelled after WW2 would have been descended from "Old Prussians" a non Germanic non Slavic. Baltic peoples that had adopted German as their language. When the Post war Polsih governments expelled these Germans, killing tens if not hundreds of thousands they were expelling the original inhabitants.