The Battle of Wizna is considered the stuff of legend amongst military history enthusiasts and Sabaton fans. There are plenty of Polish sources on the subject, but I do not speak the language and I couldn’t find anything in English that I would consider reliable.
According to the Polish Wikipedia, Tomasz Wesołowski (a Polish historian) claims that the battle was greatly exaggerated. He specifically claims that the Germans were mainly stopped by the Narew river, and that the Polish defense collapsed only a few hours after the Germans crossed it. He also states that the myth originated from communist propaganda.
I’m curious about whether Wesołowski’s claims are accurate. There do appear to be a lot of scholarly sources indicating that the battle occurred as depicted in popular culture (not that I can read them), and it seems odd that the communist authorities would play up soldiers of the Second Polish Republic without tacking in something about how the Polish command was incompetent or that the heroic Polish leader was a peasant overriding a landed, incompetent officer.
It's a lot harder to assault an entrenched or fortified position and crossing a river than it may seem. Though German command did learn from Narew for the invasion of France, they still faced similar problems crossing the Meuse and oddly similar occasions of fortified positions holding up vastly larger German units occurred in France.
You can see the general layout in this map showing the fortified bunker positions: https://upload.wikimedia.org/wikipedia/commons/7/71/Bitwa_wizna_1939.png
10 Panzer division had already begun crossing the river and occupied the town of Wizna when Guderian was ordered to do the same by Bock on 8th September. The line of resistance here were 7 heavy bunkers occupied by machine guns, anti tank guns and larger 76mm guns where Raginis was in command. Generalleutnant Schaal (10 panzer) was injured on the first day and because there were no engineers available to build pontoon bridges they could not get tanks across the Narew to assault the defensive positions, thus the 10 panzer infantry and motorised divisions simply advanced up to the river and stopped; there was no artillery or tank support, leadership was absent and so everything ground to a halt.
When Guderian arrived on 9 September he was "incensed" at the inactivity and ordered assaults on the Polish positions which due to a lack of troops pretty much could do nothing to prevent the Germans flanking and slowly overtaking each position one at a time. It was a pretty hurried exercise and by the morning of 10th there were only a few ferries getting tanks and infantry across, but this was enough to then overrun the Polish positions.
Robert Forczyk claims that the lack of crossing points and engineers to build them was by far the main point of the hold up rather than Polish defences; though what there was fought valiantly and were likely better trained than the German units.
"Assault river-crossing operations" and attacking strong-points was clearly a tactical deficiency in the German units, and the overly complicated command structure just added to this mess - these would be somewhat improved by the time Guderian et al were crossing at Sedan in France, though again, the spectacle of vastly outnumbered fortifications holding off the Germans was repeated like at Bodange where the 1st Panzer Division was held up for a total of eight hours.
On the command problems, I'll quote from Forczyk:
The fighting on the Narew also revealed that overly complicated command and control arrangements had marred the German operational performance. While Falkenhorst’s XXI Armeekorps was trying to get across the Narew, Küchler failed to direct Korps Wodrig to support this effort. When Guderian showed up, his XIX Armeekorps (mot.) was reporting directly to Bock, not Küchler. At one point, on 9–10 September, all three of Heeresgruppe Nord’s Panzer-Divisionen were milling around the Narew without much co-ordination
Case White: The Invasion of Poland 1939 Robert Forczyk
The Blitzkrieg Legend: The 1940 Campaign in the West Karl-Heinz Frieser
