I can't help you ith your grandfather but finding information about the 28th Division is a no-brainer. The 28th Division is the Pennsylvania National Guard Division. Their symbol is a redkeystone. The 28th fought the Germans in two world wars and was called the "bloody bucket" by the Germans. They fought in two closely spaced battles in the fall of 1944. In the first, the Battle of the Hurtgen Forest the 28th and several other divisions were ground up trying to eject the Germans from this densely packed woodland that had been prepared before the war with hundreds of hidden firing positions. None of the divisions were successful. After the 28th had been withdrawn from Huertgen it was sent to a quiet sector of the front so it could refit and get replacemnts. The quiet sector was in the Ardennes Forest where the 28th was shortly fighting for it life in the Battle of the Bulge. Plenty of books have been written about both these battles. For the battle of the Bulge "Dark December" by Robert Merriam.