The guard is looking at the city past the wall.
The guard is looking for the enemy.
Looking at the city does not necessarily mean looking for the enemy.
exists e1 x1 x2 x3.(n_wall(x3) & n_city(x2) & n_guard(x1) & past(e1,x3) & at(e1,x2) & Actor(e1,x1) & v_look(e1))
exists e1 x1 x2.(n_enemy(x2) & n_guard(x1) & for(e1,x2) & Actor(e1,x1) & v_look(e1))