Minas Gerais was the best possible launch pad for a coup d'état. Rio Grande do Sul had too many units, which would require a large conspiracy, Rio de Janeiro was under a tight oversight, São Paulo had an apparently legalist army general and a distinct Military Region/Infantry division and elsewhere was too weak and too far away from power. Minas Gerais had none of that. Mourão Filho was at the helm at both the division and Military Region. UDN governor Magalhães Pinto hoped to overthrow Goulart and run for President in 1965. Colonel José Geraldo of the police was on board. Together with retired marshal (being retired was a prerequisite for marshal rank) Odylio Denis and a number of subordinates they formed a kind of "revolutionary staff". One of their most important meetings was at 17:00, 28th of March on the Juiz de Fora airport. They had good contacts elsewhere. Mourão knew IPÊS, a think tank which also served as a medium of conspiratorial thoughts, and brigade-general Muricy, who at the time was powerless, occupying the Reserve Subdirectory in Rio de Janeiro. Muricy was called to Juiz de Fora and commanded the actual vanguard of the march.
In addition to this political advantage as the only state where a cohesive military-civilian conspiracy was possible, it was also blessed in its geography as it was in striking range of not one but two centers of power, Brasília and Rio de Janeiro. Brasília turned out to be a sideshow but the highest tension was in the Rio axis.

The state's geographical peculiarity is that, rather than a strip of land reaching into the interior from the coast, it is a much longer north-south stretch, almost reaching the coast but landlocked by two thin coastal states. The other states had their shape determined by the distribution of feudal-like plots bound by latitude, the sea and the Tordesillas longitude (in some of the northeast this was vertical, not horizontal). Such was the case for what would become the coastal states, but upon discovery of gold in the late 17th century, one of the measures to choke off and control the mines was to split off a wide expanse of inner land into another division, leaving two coastal territories. One was left thinly populated to serve as a "green wall", preventing any trade, and Rio de Janeiro with its natural ports became the export route for the gold.
The result of this was that in 1964 there was only a short stretch between Rio and a state border with another division's troops on the other side. Highlands were on the way but not insurmountable and they had roads for a long time. The course towards São Paulo is a straight line on easy terrain -the Paraíba do Sul valley- but it's longer. To make it even easier, the Military Region HQ was not on the state capital (Belo Horizonte) but on the major city closest to the border, Juiz de Fora, along with a regiment.

Forces in the state included:
20 thousand police, many of which took part in the rebel expeditions;
Sergeants' School in Três Corações, which refused to partake in the rebellion;
10th Infantry Regiment, Juiz de Fora;
11th "Tiradentes" Infantry Regiment, São João Del Rei;
12th Infantry Regiment, Belo Horizonte.

The plotters had different opinions on how to make their move. Mourão Filho wanted to march on Rio de Janeiro. He thought he could even just load the 10th on trucks in a Saturday night and pop up in Rio on a Sunday morning, occupy the army HQ and publish a manifesto signed by several governors. On the other hand, Magalhães Pinto and Guedes thought they could rise the whole state in rebellion (some sources even suggest a declaration of independence, and bizarrely he had named a secretary of Foreign Relations) to enter a standoff with Jango and lead other states to follow the example. This would probably backfired and the state would be defeated. In the past São Paulo, a much stronger state, had tried to take on the rest of the country alone and failed. The actual course of events was closer to Mourão Filho's vision.