This province measures 152,589 Km² and officially belonged to Bolivia, although the treaties of Mardi (1750), El Pardo (1761), Santo Ildefonso (1777) and Badajos (1801) that were between Portugal and Spain, and the treaty of La Paz (1867) that was between Bolivia and Brazil, were all based on false or rather incomplete geographical facts and tended to support latter Brazilian claims. Most of the population in this province consisted of almost savage Indians with 18,000 Brazilians and a few Bolivians, a situation like the one that had occurred in the Bolivian coastal province before the war of 1879 with Chile. Towards the end of the 19th century much of the rubber that was produced from this province was forwarded via Brazil, without any Bolivian taxes being paid, so that on the 2nd of January 1899 the Bolivians opened a Customs House at Villa de Puerto Alonso (now Porto Acre).

This angered the Brazilian settlers, who requested on the 1st May, that the Bolivian authorities retire from the province of Acre, when this was refused the Bolivians were quickly gathered and sent packing. The leader of the Brazilians was José Carvalho. A Spanish adventurer who served as Bolivian Consul at Belem called Dr. Luis Galvez Rodriguez de Arias, arrived in Acre and on the 14th July 1899 declared the Independent Republic of Acre. Eight months later a Brazilian Naval force put an end to this Republic and handed back the province to the Bolivians.

After this several well known Brazilian poets and journalists united to organise an expedition for November 1900, this group of volunteers were called the "Solimoes", they had managed to obtain help from the Brazilian Governor of Amazonas, armed with weapons and ammunition and stocked with food the expedition set out. They first captured the Bolivian launch "Alonso" which was found to contain some war-material onboard, the launch was re-named "Rui Barbosa". However, in an ensuing fight the badly trained volunteers were beaten by a numerically inferior Bolivian unit.

José Plácido de Castro, a gaucho and former professional soldier began to form a new expedition, his force of 33 "seringueiros" attacked on the 6th August 1902 the river port of Xapuri, having landed from several canoes at 5.00 a.m., after a quick fight the town was taken and a revolution was proclaimed while also creating an Independent Republic. At the town of Volta de Emprêsa a Bolivian infantry battalion of 180 men, under the command of Colonel Rosendo Rojas, was stationed, this force attacked the 70 strong Brazilian rebels on the 18th September, using a surprise attack the rebels were forced to retreat with the loss of 22 killed. The Brazilians were armed with Winchester rifles but without a large supply of ammunition, while desertions and the havoc of tropical disease eroded this initial force, however, Plácido de Castro was able to gather another force, this time of 180 men, and on the 5th October 1902 laid siege to the Bolivians at the town of Volta da Emprêsa, ten days later the town capitulated with the loss of 30 killed. Other small actions took place at Bom Destino (24th Sept. 1902), Telheiro (30th Sept. 1902) and Santa Rosa (18th Nov. 1902), all of which were Brazilian victories.

The Bolivians, under Colonel Manuel Canseco, resisted at Puerto Alonso against the increased force of 400 men under Plácido de Castro, he also had the steamship "Independencia" plus some barges so that Puerto Alonso could be blockaded by land and river. The Brazilians attacked on the 15th January 1903 and managed to take some of the Bolivian positions. The "Independencia" was loaded with 30 tons of the best rubber and it was decided that the steamship should force its way through a fortified Bolivian position so that it could sell its cargo and with the money buy extra munitions that was required to continue to struggle, this was done and by the 24th the Bolivians were forced to surrender with the loss of 50 killed and wounded. The Brazilian force had been increased to 700 men and now took up positions along the rivers Chipamanu (or Manuripe) and the Rio Tauamanu that meet to form the Rio Orton, a Bolivian army under the command of General President Pando reached the right bank of this river and it was now that the Brazilian Government stepped in to make a treaty with Bolivia that was signed on the 17th November 1903 and called the Treaty of Petropolis, through this the province of Acre was "sold" to Brazil for 2 million pounds.

( Source: "Navigator" No.10, XII / 1974, P.45-59. "Dicionario das Batalhas Brasileiras" by Hernani Donato, 1986. )