  We obtain the anomaly polynomial of strings of general 6d
$\mathcal{N}{=}(1,0)$ theories in terms of anomaly inflow. Our computation
sheds some light on the reason why the simplest 6d $\mathcal{N}{=}(1,0)$ theory
has $E_8$ flavor symmetry, and also partially explains a curious numerology in
F-theory.
