>>41372
Haven't heard of that.

Found a figure charting the many tentacles of the years-long conspiracy, though it didn't necessarily lead to a coup; it was a destabilization effort and after 1963 several conspiracies for a forceful overthrow became serious. You can see the central role of Ipes bringing together business (yellow) and military (green) interests, which then spread their influence to politicians (teal) and further down, the press, trade unions, women's and student organizations. In miscellaneous groups (white) the CCC (Communist-hunting Command) was of paramilitary nature.

Now on a central topic in 1960s military society which proved central to how events unravelled: the relationship between officers and praças (enlisted).
The “class struggle” taking place in endless strikes, peasant movements, etc. extended into the military, pitting the lower class praças against the officers, between which existed a rift - e.g. marriage was allowed for officers but praças needed a long period of service. As NCOs were at the top of their side and directly faced the rift, it was chiefly a sergeants’ movement. Their demands were internal - more reasonable career progression, reformed punishments, greater freedom in their private lives and the rights to political expression and to be elected (the Constitution was ambiguous and in the 60s the Supreme Court came to oppose it) - and external, backing other leftist demands.
Most members of this movement were “unafilliated”, with the second largest group being, surprisingly enough, integralists (who still got purged after the coup); among others there were those closer to the officers, tied to the government, tied to several communist factions, etc.

The effect of this movement was a breakdown in hierarchy and discipline, the humiliation of officers and, at its most extreme, the ocurrence of revolts, namely the Sergeants’ Revolt in Brasília (September 1963) and the Sailors’ Revolt in Guanabara (March 1964), the former an actual violent uprising that left two dead and the latter a rally/mutiny.
Many officers saw this movement as the result of infiltration and subversion in their ranks, and the government’s lenient and supportive attitude to this movement - it was part of the popular pressure strategy - convinced them it was waging an attack on the military institution itself. The Sailors’ Revolt in particular pushed them into a hostile attitude.

An important note must be made. In the Navy, an elitist, aristocratic institution, the social rift between officers and praças was strong and so was this movement. For the Army there’s a 2013 paper demonstrating that the actual, not perceived strength of the sergeants’ movement was minimal; the revolt in Brasília only involved the Air Force and Navy, and in Guanabara, only the Navy. A similar breakdown of order in the ranks had taken place in the 30s and as a result a decades-long effort in qualification, socialization and control had conquered the NCO’s hearts and minds.