North Korean teenagers and twenty-somethings are following the government’s call to leave home for coal mines and construction sites, and the country’s leader Kim Jong Un reportedly thanked them for their sacrifices in a new letter released in state media on Sunday.

Kim also used the opportunity to hit out at the U.S., saying “the imperialists’ anti-DPRK attempt to degenerate and undermine the ranks of our young people” would be in vain. 

“Vicious sanctions and pressure and tenacious ideological and cultural infiltration has vanished like bubbles in the face of this strong current” of youth mobilization, he said in the