The operation was one of the factors behind president João Goulart's departure from Rio de Janeiro and the collapse of loyalist resistance in the city; when the detachments entered Guanabara and Brasília on 2 April, the federal government had already been defeated.

Since 1963, Mourão Filho had been conspiring in Minas Gerais against the federal government, allied to his subordinate, general Carlos Luís Guedes, governor Magalhães Pinto and the PMMG, which was prepared to fight as a conventional force.

His solution was a surprise attack, gathering units from Juiz de Fora at night, entering Guanabara at dawn, arresting the president and taking over the Ministry of War.

The operation took place along the Union and Industry highway, with the most important events in the stretch between the Paraibuna river, on Minas Gerais' border with Rio de Janeiro, and the city of Areal.

The fight approached on the afternoon of 1 April, but the possibility of confrontation was interrupted by news that Cunha Melo's superior, Armando de Moraes Âncora, commander of the 1st Army, would negotiate in Resende.

The confrontation between the opposing forces, who were on the ground in combat positions but did not actually fight, was feared by local residents and reported in the press at the time as the scene of a hypothetical civil war.

Among the army there were several "traditionalist" officers, that is, untrained by the Superior War School (ESG) and unaligned with the capitalist reorganization project defended by the IPES-IBAD (Brazilian Institute of Democratic Action)-ESG complex.

[26] Minas Gerais was a convenient state for launching the coup due to the high cohesion between the generals (Mourão and Guedes) and the governor, guaranteeing the desired civilian political support.

It did not participate simply because of the command chain: its commander-general, José Geraldo, and his Chief of Staff, colonel Afonso Barsante dos Santos, were considered ultra-conservative and anti-communist and had personal connections with generals Guedes and Mourão.

[57] It was also necessary to ensure Minas Gerais' supply in case of a prolonged conflict, and to this end the Port of Vitória and the Vitória-Minas Railway were the logistical alternative through which weapons could come from abroad.

The alliance with Magalhães Pinto was an asset for his militarily weak state, as Minas Gerais would provide troops and ammunition:[60] the PMMG would remain on the border and, as soon as necessary, would defend the route to Vitória.

[70] Mourão Filho wanted to enter Guanabara by surprise and quickly depose the government, but Guedes and Magalhães Pinto had their own plan, with a different approach: the Minas Gerais forces would arrive at the border with Rio de Janeiro and await the reaction of the 1st Army.

Guedes negotiated it with military attaché Vernon Walters and CIA agent Lawrence Laser,[71][73] and Magalhães Pinto intended to send Afonso Arinos abroad to obtain recognition of the state of belligerence.

But general Mourão refused: "absolutely", as he considered the government's support scheme to be similar to a house of cards and that, at the first push, it would collapse.Guedes believed his "19-year-old soldiers" and "very poor material" would not be useful for a takeover operation.

[101] After 08:00 or 09:00 in the morning[f] the commander of the 10th RI, colonel Clóvis Galvão da Silveira, did not want to participate in the rebellion after discovering that, contrary to what he had been informed, it did not have the support of the Minister of War.

[133] It was the vanguard of Cunha Melo's forces, colonel Raimundo Ferreira de Souza's 1st RI accompanied by the 2nd Group of the Floriano Regiment, with its Command, Services and 4th and 6th Howitzer Batteries.

According to captain Audir Santos Maciel, commander of the 6th Battery, the 2nd Group had spent the day isolated in the barracks, without news of the situation, and continued with the information that they would face an uprising by the Military Police of Minas Gerais — "they tricked us into leaving".

This way, they would avoid being blocked in the defensive terrain of the border, they would be in a better position to make connections with São Paulo and Espírito Santo and they would increase the isolation of Northeastern Brazil in relation to the South.

[142] As for Kerensky, the assessment was that his role would be to withdraw without firing the first shot, delaying the advance of the Tiradentes Detachment and allowing the Sampaio Regiment to establish defensive positions on the river.

And to complete the realistic picture, the decor of the catastrophe, the opposing troops physically confronted each other, cocked their weapons and were ready to fire the first shot.To fight this campaign, Muricy had only a few hours worth of ammunition and a force made up more than half by poorly trained conscripts.

[125] According to captain Mandarino, civilians and reserve military personnel arrived from Rio wanting to join,[163] and all drivers crossing the road were asked about the forces coming from the other side.

[170] Captain Mandarino narrated what happened in the following terms:[171] General Mourão realized that lieutenant colonel Kerensky really wanted to gain time [for the arrival of the Cunha Mello Detachment] and, as a result, told him that he would have two hours to open the access road and, in front of him, gave the order to our artillery to immediately go into position and be in condition to, upon order, attack the BC's position, in support of the infantry in the first echelon, which was my company.Still according to Mandarino, with the existing shelters, dug with difficulty in the rocky terrain, and the proximity of the enemy, his company would not be safe if the artillery opened fire.

[180] Mourão Filho returned to Juiz de Fora where, at 2:00 on 1 April, he called general Amaury Kruel and found out that the 2nd Army was marching from São Paulo against Goulart.

By swearing loyalty to Muricy, it tilted the balance of forces in favor of the rebels,[186] highlighted the possibility of other troops joining the coup and the crumbling of the government's military apparatus[191] and influenced president Goulart's decision to abandon Rio de Janeiro.

The detachment protected itself by sending a flank guard made up of the 2nd Battalion of the PMMG and an anti-tank section to the west, to a station along Paraíba surrounded by high hills, through which both the highway (BR-57) and the railway pass, to block any move in that direction.

[125] According to major Cid Goffredo, liaison officer between the 4th RM and the Tiradentes Detachment,[203] from the beginning Muricy feared that a loyalist force from São Paulo could use the road that passes through Volta Redonda to reach Três Rios and interfere with the Minas Gerais axis.

Djalma Dias Ribeiro, coming from Rio de Janeiro, told Muricy what he assessed to be 2–3 infantry battalions and 2–4 artillery batteries that had passed through Belvedere; from the time he saw it, this loyalist force should be in the Areal region at the moment.

They took what would later become the "Posto do Nino" as their headquarters, set up machine gun nests at the post and on the roads, positioned dynamite ready to detonate the bridge over the Piabanha river in the center and established themselves on the hills.

[216] Returning to Muricy, Walter crossed the 2nd RI to carry his message to Cunha Melo: "I am preparing to attack, verify the veracity of the Ancora-Kruel meeting and avoid bloodshed".

The answer came from major Granja,[x] from Cunha Melo's staff, who arrived an hour later: "I have no news of this meeting (Muricy could be bluffing), the first shot won't come from me but I have a mission to defend and I will fulfill it".