His most important posting was command over the cavalry unit that served as Emperor Dom Pedro II's personal guard in the national capital, Rio de Janeiro.

Despite having served from 1864 until 1870 as a successful field commander, José Luís was repeatedly passed over in promotions and was not awarded a title of nobility.

[1] The town was the capital of Rio Grande do Sul, a southern captaincy (later province) of the Kingdom of Brazil, which at that time was politically united with Portugal.

[2][1] José Luís belonged to a wealthy family of Portuguese descent and military background, who owned ranches and large cattle herds.

In July 1823, José Luís' father, his uncle and his paternal grandfather (Field Marshal João de Deus Mena Barreto, later Viscount of São Gabriel), openly sided with Pedro I in his struggle with the Constituent and Legislative General Assembly that had been elected to draft a Constitution.

The General Assembly punished the men by removing José Luís' father and uncle from their military commands and by ordering them to leave Rio Grande do Sul.

After Pedro I dissolved the Constituent Assembly in late 1823, the Emperor rewarded the Mena Barreto and lifted the penalties imposed upon them.

On 24 September 1825, José Luís' father died fighting against rebel forces during the Battle of Rincon, leaving him an orphan at age 7.

[6] José Luís fought in small battles on 30 June and 20 July against Ragamuffins forces besieging Porto Alegre, and he saw action again on 6 September near the town of Capela Grande (today's Viamão).

The government in Rio de Janeiro had prepared against the threat and formed an anti-Rosas alliance consisting of Brazil, Uruguay (former Cisplatina) and dissident Argentine provinces.

[7] On 15 July 1854, José Luís was promoted to lieutenant colonel and transferred to the 1st Cavalry Regiment, which served as Emperor Dom Pedro II's personal guard in the national capital, Rio de Janeiro.

[13] José Luís was promoted to colonel on 2 December, receiving the command of the 4th Regiment of Light Cavalry, and was stationed to Rio Grande do Sul.

[14] A few months later, in October, he received orders to invade Uruguay at the head of a brigade composed of one infantry battalion and two cavalry corps.

Brazil expected José Luís' small force to begin operations while its main army was being brought up to full strength.

[16] A few days previously, on 20 October, Brazil's Vice-Admiral Joaquim Marques Lisboa (then-Baron of Tamandaré) had formed a secret anti-Blancos alliance with Uruguay's Brigadier General Venancio Flores, leader of the Colorados.

He was actually a kind and warm person, according to historian Gustavo Barroso, who as commander knew how to impose a strict discipline without hurting the pride of his subordinates.

[27] After the fall of Humaitá in July 1868, José Luís took part in the Pikysyry maneuver that resulted in the Dezembrada (Deed of December), a series of decisive victories over the Paraguayans.

[28] Despite his having fought and gained victories in many battles from the war's outset, José Luís was not awarded with any promotion or title of nobility, except for receiving a few, minor chivalric orders.

Caxias' view was not shared by other general officers, many of whom openly supported José Luís and praised him as a capable field commander.

[29] José Luís fared better under Caxias' successor, Prince Gaston, Count of Eu, who held him in high regard.

[31] He was appointed on 24 April 1872 to the bureaucratic position of inspector of army units stationed in the provinces of São Paulo, Santa Catarina and Espírito Santo.

José Luís remained in that position until 4 May 1878, when he was named military commander of Rio Grande do Sul, a highly prestigious post.

[35] Historian Gustavo Barroso regarded him a valorous and brave officer, the member of the Mena Barreto family who had most distinguished himself through his own merits.