A member of the Imperial Army at the age of fifteen, he climbed all the posts of the military hierarchy of his time thanks to the soldier attributes that consecrated him as "The Legendary".

He participated in the main military events of the late nineteenth century in the Río de la Plata region and is considered a hero of the Paraguayan War.

[1][2] Manuel Luís Osório was born on 10 May 1808, in lands that belonged to the village of Nossa Senhora da Conceição do Arroio (Rio Grande do Sul).

In October he was promoted to lieutenant and participated in the peace talks with the detachment of Cisplatina and recognition of Uruguay's independence, following general Lecor.

In 1835 the Ragamuffin War broke out in the province of Rio Grande do Sul, characterized by a separatist agitation which, for ten years, threatened the unity of the Empire.

Liberal-minded, Osório had sympathy for the farroupilha (raggamuffin) cause, initially fighting alongside the rebels, until the proclamation of the Riograndense Republic in 1836, when the movement took a separatist orientation, which he did not accept.

He distinguished himself in the Battle of Monte Caseros, which occurred in the suburbs of Buenos Aires on 3 February 1852, when, at the head of the 2nd Cavalry Regiment, in the vanguard of the Brazilian troops, he inflicted on the Argentine dictator the rupture of his defense device and Commands decisive operations to take advantage of success and persecution.

Promoted to brigadier-graduated in December 1856, soon after was commissioned to organize an expedition to discover rich herbs, between the rivers Pindaí and Sebolati, in the Upper Uruguay.

He participated, in charge of a division of the army commanded by Marshal João Propício Mena Barreto, of a new intervention in Uruguay to help the colorados of Venancio Flores, allies of Brazil, to assume the power in the Eastern State.

At the outbreak of the Paraguayan War (1864-1870), Osório was the most prestigious military man in the platine region, having acted uninterruptedly for 42 years in successive campaigns.

On 18 September, in the presence of Emperor Pedro II, the Count of Eu and several general officers, including Osório and Caxias, the Paraguayans surrendered after months of siege.

In command of his troops, Osório directed the march from Tuyutí to Tuiu-Cuê, advancing against the trenches and strongholds that surrounded Humaitá and protected it against enemy attacks.

Osório was replaced by General Polidoro da Fonseca and returned to Brazil to recover from his wound, he did not witness the fall of Asunción in January 1869.

On 22 March 1868, Gaston of Orléans, Count of Eu, son-in-law of the Emperor Pedro II, was appointed Commander-in-Chief of the forces in operation in Paraguay.

At the invitation of the new commander of the Brazilian forces, Osório, who had been seriously wounded in the combat of Avaí and retired to Rio Grande do Sul, returned to Paraguay, assuming, on June 6, the 1st Army Corps, stationed in Piraju, to start the Mountain Campaign.

In August 1871, Deodoro da Fonseca solemnly presented to Porto Alegre a costly sword of honour, a masterpiece of goldsmithing, carved in gold and adorned with diamonds, paid for by the officers commanded by Osório during the war.

Do not think that I am going to the Republic, or to despotism; But I will tell the noble senator that in matters of public service I do not inquire about where Brazilians stand in politics, but I do ask if they fulfill their duty for the good of the country."

In spite of having died ten years before the advent of the Republic in Brazil it is possible to know his opinion about the acts of Deodoro da Fonseca and Floriano Peixoto (both veterans of the Paraguayan War) besides having been insubordinate and betrayed the legal government they also became the first two presidents and dictators of the country: "It would be a wretch who, having fought the external enemy with the weapons of war, would then place those same weapons at the service of despotism, persecution and violence against his countrymen."

Finally, on 1 December 1993, the solemn transfer of the mortal remains of Marshal Osório began, passing through the Municipalities of Pelotas, Rio Grande and Porto Alegre.

Conceição do Arroio, the city where he was born, began to be called Osório in 1934, without popular consultation, by order of the Federal Comptroller José Antônio Flores da Cunha.