Garibaldi was born on 16 September 1840 in Mostardas, in Rio Grande do Sul, southern Brazil, to Anita and Giuseppe Garibaldi, as their first son and the only born in Brazil. At the time of his birth Mostardas was part of the revolutionary Riograndense Republic, for which his parents were fighting in the Ragamuffin War.[2] He was named after his grandfather, Domenico Garibaldi, and the Italian patriot Ciro Menotti, whom Giuseppe Garibaldi considered a martyr.[3]
In August 1862, he was present at the controversial Battle of Aspromonte, when both Menotti and Giuseppe Garibaldi were wounded in an attack by Italian troops.[6] In 1863, during the January Uprising in Poland, Garibaldi organized a legion of Italian volunteers, the Garibaldi Legion, led by General Francesco Nullo, to support the Polish insurgents in the military struggle against the Russian Empire. He accompanied his father in a trip to London in 1864. Two years later, during the Third Italian War of Independence, Garibaldi fought alongside his brother Ricciotti, father and brother-in-law at the Battle of Bezzecca, which resulted in a victory over the Austrians. His own military skill was recognised in 1867, when his father asked him to lead volunteers in an invasion of the Papal States, which ended in defeat at the Battle of Mentana.[5]