Between 1976 and 1983 the Argentine military dictatorship instituted a reign of terror known as "El Proceso" in an attempt to impose order on the country by eliminating its opponents.
As many as 30,000 were murdered, including trade unionists, political activists, rebellious priests, student leaders and intellectuals.
Most were kidnapped, tortured and "disappeared": buried in unmarked graves or sedated and thrown from planes into the Rio de la Plata.
Their mothers, frustrated by the authorities' wall of silence and intimidation, formed the Madres Movement (Mothers of Plaza de Mayo).
They have protested every Thursday afternoon since 1976 on the Plaza de Mayo to embarrass the regime into providing answers, despite the intimidation and "disappearance" of several of their own members.