in tone from the outset

Caught up in the same net with the four olds were emblems of
bourgeois art, including imported books and music as well as
modern Chinese products of the 1911–49 period. Works associated
with the Soviet bloc were castigated as revisionist. Nationalist in
tone from the outset, the Cultural Revolution’s mass mobilization
phase played up a nativist strand never far from the surface in
Chinese society. Red Guards in the northeastern city of Harbin
doggedly pulled down an entire wooden Orthodox church, a relic
of Russian influence.

First, could you tell me what is "in tone from the outset"? Or actually did I separate the sentence at incorrect point; that is, it should be "Nationalist in tone / from the outset"?

Second, I feel confused about the whole sentence although I know each word or phrase of it, but what does it mean when being put together. For example, play up and the "strand". Could you explain the sentence:

Nationalist in tone from the outset, the Cultural Revolution’s mass mobilization phase played up a nativist strand never far from the surface in Chinese society.

for me?