There are figures who seem shaped by the very territory they explored. Cândido Mariano da Silva Rondon is one of them. Born on May 5, 1865, in what is now the district of Mimoso, in the municipality of Santo Antônio de Leverger, Mato Grosso, he carried from childhood a story of loss and resilience that would become the foundation of his personality. His father died of smallpox in 1864, even before he was born. His mother passed away in 1867, when he was only two years old. He was raised first by his grandfather and later by a paternal uncle, Manuel Rodrigues da Silva Rondon, who had added his mother’s surname to his own to distinguish himself from a notorious namesake. In honor of this uncle, who raised him until he was sixteen, Cândido adopted the same surname, signing his name as Rondon.
His origins were marked by a deep ethnic blend. On his father’s side, he descended from Portuguese and Spanish settlers mixed with the indigenous Guanás. On his mother’s side, his heritage came from the Terena and Bororo peoples. This multiethnic ancestry was not merely biographical—it shaped how Rondon would view and treat Indigenous peoples throughout his life.
At sixteen, in 1881, he joined the 3rd Horse Artillery Regiment. Soon after, he enrolled in the Military School of Rio de Janeiro, where he earned a bachelor’s degree in Physical and Natural Sciences. In 1888, he was promoted to second lieutenant. During that same period, influenced by Benjamin Constant, he actively participated in the movement that overthrew Emperor Dom Pedro II and proclaimed the Republic in 1889. He was a republican and abolitionist by conviction.
The new republican government was eager to integrate the isolated western regions and Brazil’s borders. In 1890, Rondon was appointed assistant to the Commission for the Construction of Telegraph Lines from Cuiabá to the Araguaia Registry, Mato Grosso’s first telegraph line. The project was completed in 1895. From then on, his life became intertwined with the expansion of communications into Brazil’s most remote interior: he built roads, installed telegraph lines, and opened paths where no state representative had ever set foot before.
Between 1900 and 1906, he was tasked with installing the telegraph line that would connect Brazil to Bolivia and Peru. During this time, he came into contact with the Bororo people and managed to work alongside them in building the line, establishing a relationship of trust that would become his trademark. In 1906, President Afonso Pena charged him with linking Cuiabá to the newly incorporated territory of Acre. The so-called Rondon Commission, active from 1907 to 1915, would be the greatest undertaking of his career: it laid over five thousand kilometers of telegraph lines through Brazil’s forests, discovered rivers, mountains, valleys, and lakes, and had decisive encounters with Indigenous peoples previously unknown to non-Indigenous people.
One such encounter was with the Nambikwara, a group that had killed all non-Indigenous people they had previously come into contact with. Rondon approached them according to his unshakable principle: to advance always in peace, never with weapons. In September 1913, a poisoned Nambikwara arrow struck him during an expedition. He was saved only by the leather strap of his rifle. Even so, he ordered his men not to retaliate and to withdraw peacefully. His words became famous: *"Die if necessary. Never kill."*
In May 1909, Rondon embarked on his longest and riskiest expedition. He set out from Tapirapuã toward the northwest, heading for the Madeira River. By August, the team’s supplies were exhausted, and the group had to survive by hunting and foraging in the forest. Along the way, he discovered a large river between the Juruena and the Ji-Paraná, which he named the River of Doubt. They built canoes and, with great difficulty, reached the Madeira River by Christmas of that year. Upon returning to Rio de Janeiro, he was hailed as a hero—everyone had assumed he had perished in the jungle.
Throughout his career, Rondon also worked alongside former U.S. President Theodore Roosevelt in 1914, on an expedition to the River of Doubt, which was later renamed the Roosevelt River. His stance toward Indigenous peoples earned him the directorship of the newly created Indian Protection Service (SPI), founded by the Nilo Peçanha government after the 1909 expedition. He also championed the creation of Xingu National Park, a crucial initiative for the preservation of Indigenous populations. The state of Rondônia was named in his honor.
Rondon lived to be 92, passing away in Rio de Janeiro on January 19, 1958. He is the patron of the Brazilian Army’s Communications Corps. His story is that of a man who made the backlands his workplace and Indigenous peoples his allies—at a time when extermination was the norm. Marshal Rondon left Brazil not only miles of telegraph wire but an unprecedented concept of how the state should engage with those who had inhabited these lands long before any republic.