During the first two months the war was chiefly carried on in Cor-rientes, generally with heavy losses to the Paraguayans, who, however, had by August succeeded in taking one or two towns in the adjacent Brazilian province of Rio Grande do Sul. But their advancing army on the river Uruguay, numbering 7,000, was defeated at Yatay, and finally surrendered in Uruguayana to 10,000 Uruguayans and Argentines. In November following the Paraguayan army had evacuated the Argentine territory, and the close of December found the allies, 35,000 strong, at Corrales on the N. shore of Corrien-tes, ready to cross the Parana and carry the war into the heart of Paraguay. Lopez, commanding in person, was unable to defend his frontiers, and retired northward before superior forces, fighting for every inch of ground. This obstinate defence terminated with the battle of Lomas Valentinas, Dec. 25-27, 18G8, having lasted upward of three years. The war continued, however, until March 1, 1870, when Lopez was defeated and killed at Aqui-daban. (See Paraguay.) In 1866, in some provinces, especially those bordering upon Paraguay and Bolivia, great dissatisfaction with the continuance of the triple alliance and the war had been expressed, and repeated attempts made to induce the separation of some of the northern provinces from the Argentine Republic; but these disturbances were easily put down.

Bolivia, in the same year, protested against the treaty of alliance, asserting her right to a part of the Gran Chaco claimed in the treaty by the Argentine states. On Dec. 10 a convention to reform the constitution of the republic met at Santa Fe; the only important measure adopted was the renewal of the permission to congress to levy duties on exports. An insurrection headed by one Videla broke out in Mendoza, San Juan, and La Rioja, for the purpose of separating the interior provinces from the republic; it was put down in April, but the leaders escaped. The opposition to the war had been increasing in strength, and was vehemently expressed in 1868 by Alsina, governor of Buenos Ayres, who denounced the contest as barbarous, murderous, and fatal. A bill which passed congress in the same year to make Rosariothe national capital was vetoed by President Mitre. In April, 1870, a formidable rebellion broke out in Entre-Rios, headed by Gen. Lopez Jordan, the first act of which was to murder Gen. Urquiza, Jordan's father-in-law, sack his palace, and confiscate his property. Two of Urquiza's sons were murdered in Concordia; and Jordan, having forced the state assembly to appoint him governor, issued a proclamation of liberty, and appealed to the national government for immunity from punishment.

It was not until April, 1871, that the national troops, after immense losses, succeeded in quelling this rebellion. In March, 1871, the city and neighborhood of Buenos Ayres were visited by yellow fever; all business was interrupted for several weeks, and the estimated mortality during the 100 days preceding the 30th of April was 26,000. Toward the close of the year a controversy arose between the Argentine Republic and Brazil, the former having protested against alleged breaches by the Brazilians of certain articles of the treaty of alliance of May 1, 1805. But Gen. Mitre brought his negotiations to a successful termination in October, 1872; and the Argentine government was to commence negotiations with Paraguay concerning boundaries before the end of the year.