Well the premise of what I did was a 5x5x8 box. In practice the ashes would probably get compacted, and water would cause runoff - but even if you took 1% of that exercise it still comes out to roughly 7.5 miles long by 4.7 miles wide by 4.7 miles high. scattering them would work for the first maybe 100,000 but the shipping alone would be impossible during the war. I don't even want to think about mixing the ashes into other stuff though. I also don't know how much the ashes would compact. Either the dirt gets put back on top, possibly making a very large and very high hill (mountain?), or the dirt raises the elevation all across Germany.

Well the premise of what I did was a 5x5x8 box. In practice the ashes would probably get compacted, and water would cause runoff - but even if you took 1% of that exercise it still comes out to roughly 7.5 miles long by 4.7 miles wide by 4.7 miles high. scattering them would work for the first maybe 100,000 but the shipping alone would be impossible during the war. I don't even want to think about mixing the ashes into other stuff though.