The Maryknoll sisters were an order of Catholic nuns from the USA who were doing missionary work in Central America and came to be heavily influenced by the liberation theology movement. Over time they came to be increasingly persecuted by the Somoza regime in Nicaragua, which saw any kind of human rights advocacy as “communist subversion”, let alone actual radical politics. As a result, the Maryknoll sisters were pushed further to the left, with many of their students (including Ana Margarita Gasteazoro) and many in their communities joining the Sandinistas.
Once the Sandinistas had won government in 1979, a number of the Maryknoll sisters decided to move to El Salvador, feeling that their work was more necessary there. Óscar Romero, radical archbishop of San Salvador, had called on them to come before his unceremonious murder at the hands of a right-wing death squad. The US-backed regime was stoking hatred against the Church with slogans like “Be a patriot, kill a priest”, and nuns and priests everywhere were receiving death threats and regularly threatened by right-wing paramilitaries.
Four of the Maryknoll sisters: Maura Clarke, Ita Ford, Dorothy Kazel, and Jean Donovan, were assassinated by a US-trained death squad and buried in a mass grave. Five National Guardsmen were convicted for the killings in 1984 and imprisoned, but the higher-ups who ordered the attack lived a comfortable life in exile in the US for decades before finally being deported to face court in 2015 and 2016. The nuns themselves are revered today as martyrs in El Salvador.