The states under its jurisdiction originated as a distant, militarized frontier during the colonial period, with demographic development beginning around bases and fortifications along the Paraguay and Guaporé rivers.

However, in the early decades of the First Brazilian Republic, military service in Mato Grosso was stigmatized; it was a region with poor accessibility and harsh working conditions, often used as a transfer destination for dissenters and "incorrigibles".

On the other hand, officers in Mato Grosso held significant social, economic, and political influence, often participating in the frequent armed struggles for the state government during Brazil's early republican period.

[5] After the independence of South American colonies, Mato Grosso remained strategically important to Brazil as a buffer zone between the country's central provinces (Minas Gerais, São Paulo, and Rio de Janeiro) and the influences of the Platine region (Argentina, Paraguay, and Bolivia).

[14] The Mato Grosso Campaign was fought in the southern part of the province and was marked by the floods of the Pantanal, as well as hunger and disease, which exacted a heavy toll on the troops.

However, historian Mário Maestri argued that authorities had been warned in advance, there were considerable stockpiles of arms and ammunition, and the local force could have reached 6,000 troops if the National Guard was mobilized.

[14] In the following century, battles and figures such as Carlos Camisão, Guia Lopes, and Antônio João were commemorated in monuments, street names, and public buildings, and the campaign was promoted as a cornerstone of Mato Grosso do Sul's identity.

[22] After 1870, the Paraguay River was fully opened to international navigation, attracting settlers and investments to the southern part of the province, though the region also saw an increase in foreign bandit activity and land disputes.

[27] The Proclamation of the Republic was met in Mato Grosso with a small monarchist revolt by enlisted soldiers at the detachment on the Apa River's mouth on 20 December 1889.

In 1907, general Dantas Barreto criticized the "system adopted by all Republican governments of filling the ranks of the federal force there with incorrigible personnel from other garrisons".

Military personnel embodied the presence of the state in the most isolated regions through public works, mapping, border delineation, and the exploration and settlement of unknown lands.

Their presence had significant social and political importance, as military spending played a crucial role in the local economy, and the proportion of soldiers in the population was higher than in other states.

More than an economic venture, this project was strategic and had been debated since the 1870s, when the importance of railways for military mobilization in Europe and the difficulty of defending Mato Grosso were recognized.

[62] The Acre War (1899–1903), during which reinforcements from Rio Grande do Sul were sent to Corumbá (as the local garrison was deemed unreliable), confirmed to Republican authorities the need to end the region's isolation.

Clearing the dense forest for the telegraph lines required grueling treks by soldiers, often barefoot and hungry,[65] a hardship that military authorities utilized.

[66] In 1908, during Hermes da Fonseca's tenure as Minister of War, the Brazilian Army initiated the first of its comprehensive reforms during the First Republic, with two complementary measures: mandatory military service, introduced by the Sortition Law, would provide the personnel needed to complete a new order of battle.

[79] A new army order of battle, implemented in 1915–1916, reduced the planned troop strength in Mato Grosso and eliminated or transferred the 5th Strategic Brigade along with several units.

In 1939, as noted by an observer: "Campo Grande is already an important city, a convergence point for several nearby municipalities"; "uniformed personnel stand out among the civilian population", and "a respectable sum of money is injected monthly into the local economy".

[46] In May 1912, captain Antonio Netto de Azambuja led a mutiny within part of the 17th Cavalry Regiment, allegedly in support of colonel Bento Xavier's insurgency.

[96] In 1922, Mato Grosso's officer corps, including two generals (Joaquim Ignácio Cardoso and Clodoaldo da Fonseca), overwhelmingly supported the first tenentist revolt, which began in Rio de Janeiro in July.

[97] Although tenentism was a national movement rather than a Mato Grosso-specific one, local factors such as poor working conditions and punitive transfers to the region contributed to its momentum.

The conflict demonstrated the consolidation of the nation-state in southern Mato Grosso: the rebels called up reservists and looted revenue and currency issuance offices.

[105] Promises of civilian support for the tenentists were unfulfilled; since the "fusion" of rival political factions in 1921, party leaders had been content with the division of public offices and favors.

[109] However, reinforcements from Minas Gerais, led by colonel Malan d'Angrogne, defeated the incursion into Mato Grosso at the Battle of Três Lagoas,[110] forcing the rebels to move south and embark on the Paraná Campaign.

[116] The army's image in the region suffered, as conscription failed to provide adequate mobilization, and the government continued to rely on the "patriotic battalions" of the local oligarchs.

The government sought to reinforce the Mato Grosso Flotilla and sent a commission led by the Inspector of Coastal Artillery, general José Pessoa, to examine Fort Coimbra.

[133] According to his aide-de-camp, Nelson Werneck Sodré, "without boats and airplanes, it was impossible to command that Military Region, with troops dispersed across vast territory, hundreds of kilometers from the headquarters, which also lacked resources".

[134] Collaborating with the civil administration, Pessoa established schools in remote regions where Portuguese was scarcely known, gaining attention from the press in Rio de Janeiro and São Paulo.

[135] His main concern was combating banditry, which had reached its peak in the region, taking advantage of the borders and protection from local power brokers who refused to return the weapons distributed in 1932 to fight the constitutionalists.

[138] The Military Region participated in World War II through the 9th Engineering Battalion, based in Aquidauana, which was transferred to the Brazilian Expeditionary Force (FEB), along with many soldiers from other units.