What grid system did the US Army use in the Hurtgen Forest?

I am trying to map grids in US Army AARs. However, I cannot find WW2 vintage 1:25,000 or 1:50,000 maps of the Huertgen forest. The closest I can find are the 1952 series of 1:25,000 maps with UTM and Nord de Guerre grids superimposed. Am I right to believe that the UTM system was not introduced until after the war and the US used the Nord de Guerre?

 

Nord de Guerre. Notes on the "Modified British System" used on the European Theatre of Operations during the WWII

 

Thanks