27k soliders are going to get slaughtered by trench warefare tatics used in ww1 where millions died.
The only way you counter trench, is though heavy mechanized infantry in combination with Artillery and Air Bombing.
Trench completely wrecks line marching and also completely wrecks cavalry, also makes heavy armor useless as well, as once they fall in trench that is the same as saying "GG".
This is why it was so effective up til the end of WW2 even, until one side had completely Air superiority.
But once we had cruise missiles, and napalm bombs, trench became more of a death trap then a tatic.