Nevertheless, there is a queer quality in that time [the
Middles Ages]; which, while it was international was also internal and
intimate. War, in the wide modern sense, is possible, not because more men
disagree, but because more men agree.

Under the peculiarly modern coercions,
such as Compulsory Education and Conscription, there are such very large
peaceful areas, that they all can agree upon war. In that age men disagreed
even about war; peace might break out anywhere. Peace was interrupted by feuds
and feuds by pardons. Individuality wound in and out of a maze; spiritual
extremes were walled up with one another in one little walled town; and we see
the great soul of Dante divided, a cloven flame; loving and hating his own
city. – GK Chesterton