Hello Christoph!
I took a chance and wrote the Eisenhower Museum today to see if they have the records on the 2 outfits you mentioned above - that is the 15th FA Bn and the 299th Combat Engineers. I have asked the gentleman there so much in the past and he has been terrific, so while I did not want to bother him, it does seem like the easiest approach. If they do not have the records, I can then take another step, which maybe I will just quickly see if there is an Association for these groups.
Yesterday I did write the 78th Division, Flash News contact, to see if I can advertise that I am looking for folks involved with the liberation of Waldbrol or those who were prisoners, and also if there is anyone that knew anything about Siegburg.
In some of my notes Dad and Gidrie were on the run/loose for 4 days before getting lucky with that farmhouse where they stayed for 2 days. So the dates were the 15th, escape, and the 21st, free at last. How far did they get? Maybe soon we will find out.
Thank you again for that last lead!
Jean J