Roman battlefield found deep inside Germany

[caiusbeerquitius]

I just had a talk with Prof. Dr. Ubl about this on the phone. We agreed upon that we in fact cannot be sure that Romans were involved in this fight at all. In the light of the findings from the northern bogs as well as this specific article ([url:2nedy7il]http://www.illerup.dk/documents/illerup_81.pdf[/url]) it may very well be the case that this are the remains of German tribal fighting.

After leaving Mogontiacum and crossing the Rhine his first goal was probably to secure the Roman territories east of the river, the northern part of Agri Decumates. Then attacking the Germanic settlements near modern Kassel, which is just around 100 km away from the Wetterau, the most northern tip of Rome's territories east of the Rhine. The route was used regularly by Roman armies campaigning against the Chatti since Drusus times. If the Germans had deserted their settlements as described by Herodian, Maximinus could have decided to pursue them further north. Kalefeld is around 70 km away from Kassel, so only a few day marshes.

Geography: How do we know those exact places Maximinus went to (Kassel, e.g.)?
Is this based on some sound facts / texts?
I think it is more plausible to first of all expect German tribal fighting, especially in regard of the size of the battlefield. The presence of Roman objects at the site does not necessarily imply Roman presence. However, Roman presence cannot be ruled out as well.