The rule of Rivadavia was of great value to the country. He reformed the laws and administration, introduced wide and somewhat drastic ecclesiastical changes, established the University of Buenos Aires, and, in general, pursued an enlightened and progressive policy.[49] But the country was divided into two hostile parties, and neither being prepared to tolerate the triumph of the opposing system, the position of Rivadavia was rendered very difficult. He belonged to the Unitarian party, and its members have succeeded in maintaining their system, which aimed at a Republic with merely municipal local government. Buenos Aires was to be the administrative centre and to control every province, and thus to hold the position which Paris occupied in France. But the propertied classes in the interior belonged chiefly to the Federalist party. They viewed with suspicion the oligarchy of office at the capital, and advocated a federation on the model of the United States. At first Rivadavia held his ground against his active opponents, led by Manuel Dorrego, who were eagerly looking for an occasion against him; and this was speedily found in a foreign war.

Uruguay has been united to Brazil, but in 1825 it revolted against the Emperor, and, as might have been expected, Argentina took the part of her neighbour, and Brazil declared war. Assisted by Admiral Brown, an Irishman, the Argentines inflicted great loss upon Brazilian shipping, and Alvear took command of a large army, which invaded Rio Grande do Sul and completely defeated the Brazilians at Ituzaingo on February 20, 1827. This blow was decisive, and a treaty was made by which Rivadavia, distracted by domestic troubles and anxious to secure peace at any price, agreed that Uruguay should still remain a part of Brazil. His enemies had already spared no efforts to rouse prejudice and inflame public resentment against him. Appeals had been made to provincial jealousies, the issue of paper-money was alleged to be draining the country of the precious metals, and even his statesmanlike efforts to encourage immigration and the hospitality he offered to foreigners were matters of accusation against him. The treaty raised a storm of indignation, and had to be annulled. Rivadavia was so completely discredited by this transaction that on July 7, 1827, he was forced to resign, and thus the country lost probably the best constructive statesman she has produced—a loss which she could ill afford.

Dorrego succeeded him, but in reality the Republic was showing a strong tendency to split up, and Lopez in Santa FÉ, Ibarra in Santiago, Bustos in Cordoba, and Quiroga in Cuyo, possessed almost as much power as Dorrego at Buenos Aires. However, with the help of several of these men, he succeeded in ending the war by a compromise which left Uruguay an independent state. Argentina was thus free to devote herself to domestic warfare.

Lavalle was now the head of the Unitarians, and he succeeded in expelling Dorrego from Buenos Aires. The latter fled to his estates and raised a body of adherents, but was captured and shot by Lavalle. The death of Dorrego cleared the way for a man who was destined to have a much longer political life than is usual in South America, and also to fill a much larger space in the eyes of the world. That man was Juan Manuel Rosas.

Darwin records that he and the well-wishers of Argentina were looking with satisfaction and hope at the vigorous measures and rapid advances of this remarkable man, and he also adds in a note written years afterwards that these hopes had been miserably disappointed. Rosas was a rich man, and from his earliest days had been engaged in cattle-raising on the southern Pampas. In this hardy open-air life he had greatly distinguished himself by his boldness and skill in riding, and was the idol of hundreds of half-savage Gauchos. He was not endowed with signal abilities, but he was a hard, practical man, full of audacity and little troubled by scruples. He was now the chief of the Federalists, but at first there seemed little prospect that he would be able to make head against Lavalle. The latter led an army to attack his enemies in Santa FÉ, while General Paz marched upon Cordoba, and at the same time they sent some veteran troops to operate against Rosas in the south. But these were overthrown by the hardy horsemen of Rosas, and he came to the rescue of the Federalists. General Paz had captured Cordoba, and defeated Quiroga with heavy slaughter, but Rosas' weight turned the scale. He marched to Buenos Aires, and in June, 1829, Lavalle, who had become involved in a dispute with the French Minister, was glad to resign and leave the country. His successor, Viamont, was a puppet of Rosas.

On December 8, 1829, Rosas was elected Captain-General in the interests of the Federalists, but he had no intention of allowing Federalist principles to stand in the way of his supreme rule. Lopez was despatched against Paz, who had the misfortune to be accidentally taken prisoner. Showing unusual magnanimity, Lopez spared his life. The troops of the Unitarians never recovered from the loss of their brave leader, and being attacked by the ferocious Quiroga and driven to Tucuman, they were in a hopeless position. Quiroga butchered five hundred prisoners in cold blood, and few of the remnants of Paz's army escaped to Bolivia.

Rosas then employed himself in consolidating his power at Buenos Aires, and with this object he repealed several of the Liberal laws of Rivadavia. In this task he was assisted by a clever and crafty man named Anchorena, with whose collaboration he passed a rigorous law of "suspects" directed against the Unitarians. Severe as he was against that party, and detested as he was by the late holders of office in the capital, who resented the dominion of a rustic, he was really, by his masterful measures, advancing the principle against which he posed as the nominal antagonist.[50] At the end of 1832 his term of office came to an end, and he was re-elected. But as his extraordinary powers were not renewed he haughtily refused office, and left Buenos Aires to reduce the Indians of the Pampa, who had taken advantage of the civil discords of Argentina. Again a man of straw was put at the helm. His name was Balcarce.

In the Indian war Rosas was successful, penetrating as far as the Rio Negro and destroying, according to his own computation, twenty thousand of the enemy. It is not necessary to describe the manoeuvres and hesitations which preceded his return to nominal as well as real power. In 1835 he accepted the title of Governor and Captain-General, and henceforth ruled as a military Dictator. Never was there a more ruthless tyrant. The two most prominent soldiers and possible rivals left in Buenos Aires were Quiroga and Lopez. Quiroga had seen the elevation of Rosas with ill-concealed disgust, and the new Dictator resolved to make away with him. Rosas, therefore, commissioned him to go to pacify Salta and Tucuman, and on his way thither caused him and his suite to be assassinated. Shortly afterwards Lopez died, and it is only necessary to say that his physician was handsomely rewarded by Rosas. He established a reign of terror, and formed a club of ruffians called the Massorca, whose business it was to murder his enemies. One Maza attempted a Parliamentary resistance to him, and the crafty Dictator, after the plan had failed, first lulled him into security by vague promises of safety and then sent four men to stab him to death. His death was followed by an extensive proscription; in fact, the history at this period is distinctly Tacitean.

The power of Rosas was the greater because he had the help of a skilful general named Urquiza, against whom none of the Dictator's many enemies could make head. For a long time his power was unassailable, for the poignards of the Massorca were ready to repress any opposition, and even the Church was powerless against him. He expelled the Jesuits, paying a tribute at the same time to "their Christian and moral virtues," but declaring that they were opposed to the principles of government. Undoubtedly they were to the principles of his Government.

One of the main features of his policy was jealousy of foreign influence. He decided that all children born in Argentina were ipso facto citizens and liable to military service, and this decision remains in force at the present day. It led, however, to endless trouble with France. It is probable that if he had been able Rosas would have closed the country to all foreign nations, as his brother-tyrant, Francia, did in Paraguay.

But the old Greek saying that the worst disease of tyranny is the impossibility of reposing trust in its friends was to be justified, and Urquiza, his right-hand man, who had crushed the invaders from Uruguay at the battle of India Muerta and who had overawed all opposition, was at last to prove faithless. He had long been established as Governor of Entre Rios, where he had acted with remorseless cruelty in stamping out disaffection. His first attempts to subvert the authority of Rosas were unsuccessful, but in 1851 he made an alliance with Brazil and one of the Uruguayan factions, and in the December of that year he assembled a force of twenty-four thousand men, crossed the Parana, and marched into Santa FÉ. On February 3, 1852, Rosas was overwhelmed at the battle of Casseros near the capital and he fled to Europe. Twenty-five years later he died in Hampshire.

Rosas disappeared unregretted. Although it is possible that at the time he came to the front a military dictatorship was the only possible form of government, yet he was one of the worst of the long list of South American tyrants, and it is probably impossible to find any redeeming feature about him except the fact that he encouraged agriculture—a service which was largely neutralised by his hatred of foreigners and foreign commerce. Undoubtedly he stopped the progress of a promising country, not only for the twenty years of his remorseless tyranny but for the long years which were required to recover from the effects of his sanguinary and soulless domination.[51]

Anxious as all were for peace and constitutional government, there was some civil warfare and much dissension before the position of Urquiza could be secured. Finally, on May 1, 1853, the Constituent Congress drew up a Federal constitution, and this is practically still in force.[52] Hardly less important was the treaty of the 10th of July following, made with England, France, and the United States, which declared that the Parana and other rivers should be for ever open to navigation.

Urquiza was elected the first President under the new constitution for a period of six years, and the country began to recuperate. The port of Rosario sprang into being, and the other river cities rapidly doubled in population. But towards the end of Urquiza's term civil troubles were renewed. The Province of Buenos Aires had been left outside the Confederation and was in a position of antagonism to the other Provinces. The party of the capital was called the PorteÑos—the men of the Port—and they took the place of the old Unitarian party. In 1859 Buenos Aires actually declared war upon the Federal Government, but Urquiza defeated its forces. Before a settlement could be made his term of office expired and he was succeeded by Dr. Durqui. Fortunately, the Governor of Buenos Aires, Bartolemo Mitre, was a true patriot, and though he was obliged to make war upon the President his efforts were directed to settling the Federal question, and they were, for the time, successful. Urquiza evacuated the capital and retired southwards. Mitre followed him with a large army, and in October, 1861, defeated him at Pavon and himself became President.

It would have been well if the energies of Mitre had been left unhampered to settle the thorny question of the respective claims of the PorteÑos and the provincials, but it was the misfortune of Argentina to be suddenly involved in the most serious foreign war of its history. This was the great Paraguayan war.

The occasion of the hostilities was Uruguay. That country had long been distracted by the savage political strife of the Colorados and Blancos, and in 1864 the Blancos, having got the upper hand, elected Dr. Aguirre to the Presidency, who, by his rigorous measures against all suspected of disaffection, excited the resentment of both Argentina and Brazil. Both of these countries had important stock-raising interests on the Uruguay frontiers, and in the civil turmoil their subjects were frequently subjected to extortion and plunder. Having incurred the hostility of its too-powerful neighbours, Uruguay looked about for an ally, and found one in General Lopez, the Dictator of Paraguay.

Lopez in his youth had visited Europe, admired the great armies of the Continent, and returned convinced that he might play the part of Napoleon in South America. He had still hardly reached middle age and was able, cruel, and obstinate. He devoted all his efforts to raising and equipping an army by which he hoped to make himself the arbiter of South American politics. Accordingly he welcomed the appeal of Uruguay, and declared that he would regard an invasion of Uruguay by Brazil as an unfriendly act. When Brazil attacked Uruguay he did not, indeed, hasten to fulfil his promise; he cared nothing for the Colorados or Blancos, and the difficulties of invading Brazil were at first insuperable, but he was awaiting a favourable opportunity for his own aggrandisement. As far as Uruguay was concerned the Brazilians soon settled the matter; they beat down all resistance, set up Flores as President in February, 1865, and having established good relations with Montevideo, withdrew their army. But Lopez was a more difficult problem.

Lopez had already declared war; he had attacked Brazilian ships and made preparations to invade Rio Grande do Sul. His main object was to crush the Brazilian troops in the Plate district before they could be reinforced. His plans were bold, but there appeared no reason why they should not be successful. He had forty-five thousand infantry, ten thousand cavalry, and adequate artillery. Another fact in his favour was the friendship of Urquiza, now Governor of Corrientes, who was the enemy of Mitre. Both Brazil and Paraguay requested permission from Mitre to march their army through Misiones, but the President wished to remain neutral and refused both requests. Lopez, however, was dismayed by no obstacle, and directed General Robles with twenty-five thousand men to invade Corrientes. They soon overran the province. Argentina was in an awkward position, for her regular army amounted to six thousand men only, but she had the support of Brazil and Uruguay. On June 2, 1865, the defeat of the Paraguayan fleet by Brazil at Riachuelo baulked Lopez's schemes of an offensive war, and the allies prepared to invade Corrientes. Lopez was further hampered by the defection of Urquiza, who finally refused to assist him.

The plan for the invasion of Rio Grande had not been abandoned, but the Paraguayan force was opposed by that of Brazil and Uruguay on August 17th, and suffered defeat. A month later the defeated army under Ertigarribia surrendered. Before the end of the year Lopez was compelled to evacuate the Argentine territory.

But his position was less unfavourable than might be supposed upon a comparison of the resources of the contending countries, for he had an excellent army and the country between the Parana and the Paraguay was admirably adapted to defensive operations. It was densely wooded and liable to floods which often made it impassable. As long as he could hold Humaita, where he had erected batteries to stop the Brazilian fleet, it would be impossible for the allies to make an effective advance. They had an army of forty thousand men concentrated near the town of Corrientes, and by April, 1866, they had forced the passage of the Parana and were in Paraguay. On May 24th they were attacked by twenty-five thousand Paraguayans and a desperate battle ensued, which ended in the victory of the allies. The Paraguayans lost five thousand killed and wounded, and their opponents, who lost about two thousand, were so severely crippled that they could not advance upon Humaita—a movement which might have ended the war.

The army was devoted to Lopez and the Paraguayan made a fine soldier, while the allies, encamped in unhealthy swamps, lost heavily from disease. Mitre at last began an onward movement, but on September 22nd he was repulsed with great slaughter at Curupaiti, and the war came to a standstill. There was a long pause, for the difficulties of the allies were enormous and cholera broke out in their camp. It was not till November, 1867, that the Brazilian army succeeded in crossing the Paraguay north of Humaita, and this clever movement of the Brazilian Marshal Caxias decided the fate of the war. The allied armies began to close round Humaita and Brazilian warships forced their way beyond Curupaiti. Lopez fought with remarkable determination and skill, but his embarrassments rapidly increased, and on February 18, 1868, the Brazilian fleet ran the batteries at Humaita, and this entirely disorganised the transport system of Lopez, who relied chiefly upon his waterways. All through the year fighting continued, but on December 27, 1868, Lopez received a crushing defeat at Angostura, south of Asuncion, and he was compelled to fly into the interior. A few days later the Brazilians occupied Asuncion. But the irrepressible Lopez proclaimed a new capital at Peribebuy and made desperate efforts to carry on the war. After much fighting the allies succeeded in capturing the town in August, 1869, and pursuing Lopez, defeated him at Campo Grande, the last pitched battle of the war. He fled into the forest with his mistress, Madame Lynch, his children, and numerous faithful followers. Even in this extremity he still kept the field, until at last, on March 1, 1870, while he was encamped far to the north on the river Aquidaban, his men were thrown into a panic by the approach of the enemy. In the confusion Lopez and his staff attempted to escape, but the General's horse stuck in a swamp; he refused to surrender, and was killed by a spear-thrust. Thus died this extraordinary man, who had wantonly led his country into a war in which five-sixths of her population perished.

During this long war the domestic history of Argentina was uneventful. Brazil was far more prominent in the war than Argentina, for General Mitre was several times distracted by rebellions in the north-west which called him from Paraguay. The rebels were easily driven across the Andes. But the constitutional question had never been settled, and hostility to the PorteÑos became stronger. The influence of Mitre had waned, and in 1868 Sarmiento was quietly elected in his place.

The close of the Paraguayan war is also the close of the anarchical period of Argentina's history. Hereafter, though she was often to be unwisely governed, the worst of the wars and revolutions were at an end, and the people were to devote themselves to developing the natural wealth of the country. Since the Revolution, her history had been almost as bloodstained and turbulent as the worst of her neighbours, but henceforward peace and prosperity, though not uninterrupted, are to distinguish her from the other South American Republics.