The assault battalions were comprised of only unmarried volunteers 27 and younger.

They suffered extremely high casualties.

When the entire army was trained as shock troops, the high command discovered that husbands, fathers,and grandfathers didn't fight as hard as the young single men.

They wanted to live.

SO THE TACTICS WERE CHANGED IN ORDER TO SAVE LIVES.

See?

Even with new tactics, the Germans did extremely well.