The artists used their work to convey their disdain for the Soviet regime and against the use of violence but did so with humour and charm, and always subtly enough to get past the censors.
They also shunned conventional layouts and hierarchy by integrating type and graphics rather than viewing them as separate elements. It may have been partly because fonts weren't available, so every letter was hand-drawn.
Henryk Tomaszewski, who's the founding father of the Polish School of Posters, forged a deal with the Communist state, which changed the course of modern graphic design. Approached by the Ministry of Arts and Culture to design a film poster, he said he would only do it if he was given complete artistic free rein.
They agreed. The only rule was that he, and subsequent poster artists, must not do things the way they were done in the West. And as long as the artists avoided politics, they were left to their own devices.