Subject of Wielun bombing on the 1st of September 1939 is insignificant to any historian or author writing about Luftwaffe operations during 1939-1945. At the end how many bigger towns with greater importance were bombed in WWII? So that subject is not properly investigated by any of them. After reading several books about Luftwaffe, I have an impression that they just repeat the same stories without even bother to investigate further when talking about Wielun. How much time are you willing to spend on Wielun when you write a book covering 5 year of combat operations?
So I found many sources contradicting each other or even the same authors contradicting themselves when it comes to Wielun bombing.
For example Horst Boog writes that German reconnaissance located a Polish cavalry brigade and Polish infantry division in or around the town on 31st of August. And based on that report Germans concluded that Polish HQ's might be in town. That is all reasonable assumption. Marius Emmerling writes that Polish 28 Infantry Division HQ was in Wielun and town was an important communication center. So on the 1st of September 1939 early in the morning StG 76 bombed the town to take care of Polish units in the town, HQ's and to disrupt communication. Out of the sudden he goes about a fog and German pilots missing their targets and bombing town by mistake. Emmerling states that some Ju87 were damaged by anti-aircraft fire from the ground during Wielun bombing. Then both Boog and Emmerling say further that bombing of Wielun was a "tragic mistake".
You have done reconnaissance, agreed on target and bombed it. And than what? You bombed your target by mistake because of the fog? That does not have any sense.
Otto Schmidt from StG 76 describes clearly his actions when talking about diving from 2500 meters and hitting targets in the city centre. He seems to see everything clearly on the ground. No mistakes, just hitting targets.
Then apparently there were many more bombing of the town. Records show StG 2 and StG 77 bombing in the early afternoon. Lt. Lehmann from StG 77 describes Polish military targets in the city centre and in roads to/from the town. Oskar Dinort from StG 2 in his report does not have much problem with identifing military targets in the town and even drops bombs from 800 meters!
So after hitting targets by mistake in the morning because of the fog, Germans came back over the town again, noticed military targets and hit them again and again - no fog or mistake this time? In some books authors only mention afternoon raids, not a word about morning ones.
I also read some explanations that Wielun was bombed by some bombs that missed targets. That sounds like authors don't know what they are talking about, didn't bother to look at the Wielun pictures taken by Germans after the bombing and forgot to check the area's maps. I could understand missing targets when bombing is done from high altitude by He111 for example, but not by dive bombers Ju87, where highly trained pilots are supposed to miss targets by tens of kilometers according to those authors. When you dive on the target, you hit the target or very, very close. Simple as that.
So according to many reputable historians, Wielun bombing is about a fog, mistakes and bombs falling randomly. Funny that this comes from some German, English or US historians, not Polish ones.
Polish version of events seems to have more respect for skills of German pilots and quality of Luftwaffe operations than most of the other ones.
Only two facts are now undisputable, I think:
1. German units bombed Wielun repeatedly on the 1st of September 1939 as a military target they thought it was.
2. Polish cavalry brigade (some early German reports were saying was destroyed in Wielun) was not sitting around in Wielun city centre on the 1st of September, but was busy stopping tanks of German 4 Panzer Division 35km to the south west from Wielun. There are Polish reports in English that it was hit there several times by German bombers in or around Mokra village.
Wielun being a military target because of military presence in or around the town was also confirmed by German courts after the war when it rejected Polish claims about Wielun not being a military target.
Pity that apparently highly reputable historians invented bombing by mistake and target missing bombing. There are no facts to confirm this. According to German pilots reports they could see everything clearly from the above in Wielun.
When I looked at Wielun bombing in Wikipedia, bombing by mistake in the fog and missing target bombing is there in English language as an alternative to Polish version of events. It does not look professional at all, contradicts official German court ruling and is a bit of a joke really. From German point of view Wielun was bombed as a military target, not by mistake or some random falling bombs. You can't have both ways in the same time. This defies logic and should be corrected. There is no version in German language at all. Strange, as this subject seems to come back from time to time on different forums, not only in English language.