A friend of Humberto de Alencar Castelo Branco since he was a teenager at the Military School of Porto Alegre, he participated in the 1930 Revolution and fought in the FEB as head of the 2nd Section (information) of its General Staff.

In the early 1950s, he supported the right in the political dispute at the Military Club and in 1954 he contributed to the downfall of João Goulart, then Minister of Labor under Getúlio Vargas, but in the following year they became personal friends.

He participated in the conspiracy of São Paulo governor Ademar de Barros with various disgruntled sectors, including the Communist Party, for a "countercoup" against Castelo Branco, but it was unsuccessful.

According to statements by Ernesto Geisel and general Rubens Restell to journalist Elio Gaspari, Jango also managed to obtain public funding for a coffee farm in Espírito Santo.

[2] In 1923, when he was first lieutenant in the 7th Cavalry Regiment, in Santana do Livramento, he participated with other soldiers in demonstrations in support of the Federalist Revolution, condemning the fifth consecutive re-election of Borges de Medeiros.

[2] Nelson Werneck Sodré accused Kruel to be one of the officers who abused their positions in the election of the Military Club's directorate in 1952, persecuting supporters of the Yellow ticket.

[19] In July one of the prosecutors, Amador Cisneiros de Amaral, protested that prisoners were being held into solitary confinement for longer than the legal maximum period of three days.

[20] In February 1954, when commanding the 1st Guards Cavalry Regiment (Independence Dragoons) in Rio de Janeiro, Kruel was the first of 82 signatories of the "Manifesto dos Coronéis" and was responsible for delivering it to the Minister of War.

The document criticized the administration of Getúlio Vargas, the lack of resources for the army, the living conditions in which the soldiers were left in, and the 100% increase in the minimum wage proposed by Minister of Labor João Goulart.

Kruel had become the youngest brigadier general in March,[2] commanding the Divisional Artillery of the 1st DI,[d] the 1st Cavalry Division and, after July 1955, the Chief of Staff of the Southern Military Zone.

[25] Kruel took office promising to moralize the institution and repress the growing violent attacks against property in Rio de Janeiro, with the order to shoot the assailants who resisted.

[27] Kruel also created the "Turma Volante de Repressão aos Assaltos à Mão-Armada"[e] (TVRAMA), consisting of seven police officers from the Special Diligence Section (SDE),[f] led by detective Eurípedes Malta, directly under his command.

[37] Kruel participated in a meeting of generals in Rio de Janeiro, demanding that Minister of War Odílio Denys accept whatever solution the National Congress might have for the crisis.

Kruel maintained Goulart's mandate in the army, devising a defense scheme, isolating the conspirators who subverted the government and ensuring the obedience of various military currents.

Kruel simply suggested closing Congress, restoring the lost presidential powers to parliamentarism negotiated by congressmen, and passing the base reforms proposed by Goulart via decree.

In June–July 1962, Kruel engineered military pressure on Congress in the interval between the end of the parliamentary cabinet of Tancredo Neves and the beginning of that of Brochado da Rocha.

The new cabinet was more suited to Goulart's goal, to bring forward the plebiscite to restore his presidential powers, and Kruel was one of only two military names preserved by the new ministry.

Jacob Gorender and Moniz Bandeira, the latter based on accusations made in O Semanário, described these events as part of a maneuver for Lacerda to react violently to the demonstrators, justifying federal intervention in Guanabara and the neutralization of its governor.

[2] Since his resignation from the Ministry of War, he spent months without talking to Goulart, displeased, until he was surprised in December when the president called him to command the 2nd Army, in São Paulo.

[2] The American ambassador, Lincoln Gordon, through the military attaché Vernon Walters, brought Kruel and Castelo Branco, now one of the main conspirators, closer together after decades of rupture.

[66] The 2nd Army would be the "scale tipper" in the overthrow of the president Goulart, whatever its position;[67] for Castelo Branco, the joining or not of São Paulo to the conspiracy was the difference between a calculated risk and an adventure.

[71] That same day, Olímpio Mourão Filho, conspirator and commander of the 4th Military Region/Infantry Division, in Minas Gerais, went to Rio de Janeiro, where he obtained a guarantee from Riograndino that he would not have São Paulo against him.

[80] At 16:00 or 17:00[h] Kruel called an evening meeting with his generals—these three and Lindolfo Ferraz Filho, from the Divisional Artillery of the 2nd DI, and Carlos Buick Júnior, from the Military Garrison of Santos.

In Moreira's laboratory, Kruel had a secret meeting with Raphael de Souza Noschese, president of the Federation of Industries of the State of São Paulo (Fiesp), receiving six suitcases of money with a total of U$1.2 million.

[81] The former would only return from vacation three days later, upsetting Kruel,[83] while the latter avoided the meeting and went to his headquarters in Caçapava to prevent the participation of the regiments from the Paraíba Valley in the coup.

[88] In his second call, at 22:00, and in the last, around midnight, in the presence of the generals, Kruel offered his support if Goulart closed down the CGT and other popular organizations, intervened in the trade unions and removed the auxiliaries most associated with radicalism, such as Abelardo Jurema, Minister of Labor, and Darcy Ribeiro, from the Civilian Cabinet.

[118] Kruel was one of the supporters of the "cleaning operation", articulating, together with the Department of Political and Social Order, the immediate arrest of leftist leaders, especially of the CGT, starting on 1 April.

[119] The National Truth Commission named Kruel as one of those responsible for "managing structures and carrying out procedures aimed at committing serious violations of human rights".

Kruel, whose loyalty the government already doubted, made no objection and personally handed over the copy of the Diário Oficial da União with the act of removal, keeping the 2nd Army in readiness.

On 11 August, Kruel launched a manifesto against the dictatorship, calling the recent impeachments "an instrument to elect candidates of the personal liking of the head of the Executive branch".