Declassified documents from Argentina's dictatorship reveal that in July 1983, the SIDE conducted a comprehensive political, ideological, and military analysis of various leftist organizations, including the Montoneros, the Revolutionary People's Army (ERP), and the Communist Party (PC). The documents indicate that the intelligence agency had deeply infiltrated guerrilla and human rights organizations, highlighting a significant effort to understand the rifts within the Argentine left throughout its history.

The analysis, over 500 pages long, describes the Montoneros as a fusion of revolutionary left Peronism and progressive Christian movements influenced by Marxism. The SIDE identified these groups as threats to national security, noting their ambition for political power through armed struggle, as stated in their core objectives of political takeover.

This information sheds light on the lengths to which the dictatorship’s intelligence services went to monitor and disrupt leftist movements. It also underscores the oppressive climate of surveillance and political repression that characterized Argentina during this tumultuous period, particularly against those movements advocating for social justice and change.