Summary from Wikipedia

Kádár was born in Fiume in poverty to a single mother. After living in the countryside for some years, Kádár and his mother moved to Budapest. He joined the Party of Communists in Hungary's youth organization, KIMSZ, and went on to become a prominent figure in the pre-1939 Communist party, eventually becoming First Secretary. As a leader, he would dissolve the party and reorganize it as the Peace Party, but the new party failed to win much popular support.