In 1820 the standard of revolt was raised in Cadiz against the Spanish Bourbons, who, with the aid of the Holy Alliance, had re-established absolutism after the fall of Napoleon. The feeble Ferdinand was compelled to accept a liberal constitution. When the news reached Lisbon the Regency, acting there for King John, was panic-stricken. Communication with Spain was forbidden and word sent off post-haste to John to urge his immediate return to Portugal, or at least the sending of his eldest son, as the only means of pacifying the deep dissatisfaction felt because of the absence of the Court and government. In Porto—always the centre of liberal movements—a formidable conspiracy was formed which included the leading citizens and the officers of the garrison, and in August, 1820, the royal authority was overthrown after scarcely a show of resistance, and a provisional junta installed. The movement spread over the northern provinces and thence to Lisbon, where a junta assumed power in December. After some confusion it was agreed temporarily to adopt the Spanish Constitution, to summon the Cortes, and to retain the Braganza dynasty as constitutional monarchs.

The news of the rising in Porto spread like wildfire through the Portuguese possessions beyond sea. Madeira and the Azores immediately installed revolutionary juntas, and some of the Brazilian provinces could not wait until the assembling of the Cortes before establishing free governments. Among native Brazilians and immigrated Portuguese, among soldiers and citizens alike, the enthusiasm for a constitution was well-nigh universal. In ParÁ, Pernambuco, and Rio Grande do Sul, the royal governors were dispossessed by the united soldiers and people, and the Spanish Constitution proclaimed as the law of the land. Rio, however, lay quiet, and it was not until February, 1821, that the Bahia garrison deposed the governor, and installed a provisional junta, which, protesting allegiance to the House of Braganza, proclaimed the Spanish Constitution, nominated deputies to the Cortes, and promised to adopt whatever definite constitution might be framed by that body.

The action of Bahia was decisive. Throughout the interior it met with approval. That John could hope for no support from Brazil in case he decided to make a struggle against the Portuguese revolutionists, was evident. Reluctantly he issued a proclamation announcing his intention to send Dom Pedro, his eldest son, to treat with the Cortes, and he promised to adopt such parts of the new constitution as might be found expedient for Brazil. To such delay native Brazilians and the Portuguese-born were alike opposed. In Rio the troops and people arose, demanding an unconditional promise to ratify any constitution the Cortes might adopt. On the 26th of February a great crowd assembled in the streets, and while the cowardly King skulked in his suburban palace, the Prince Pedro addressed the people, swearing in his father's name and his own to accept unreservedly the expected constitution. The multitude insisted on marching out to the King's palace to show their enthusiastic gratitude. Trembling with fear John was forced to get into his carriage, and the miserable man was frightened out of his wits when the crowd took the horses out to drag him with their own hands. He fainted away and, when he recovered his senses, sat snivelling, protesting between his sobs his willingness to agree to anything, and sure that he was going to suffer the fate of Louis XVI.

Thereafter Dom Pedro, though only twenty-two years old, was the principal figure in Brazil. He resembled his passionate, unrestrained, and unscrupulous mother rather than his vacillating, pusillanimous father. He had grown up neglected and uncontrolled in the midst of his parents' quarrelling and the confusion of the removal to Brazil, receiving no education except that of a soldier, and hardly able to write his native tongue correctly. He was handsome, brave, wilful, arrogant, loved riding and driving, was eager and shameless in the pursuit of pleasure. His manners were frank and attractive and he was active-minded, quick to absorb new impressions, enterprising, strong-willed, loved popularity, and intensely enjoyed being the principal dramatic figure in any crisis. His personal courage was unquestionable, and he was prompt of decision in the face of dangers and difficulties. While capable of warm friendships and with strong impulses of devotion and gratitude, he lacked real faithfulness. Between him and his father little love and no sympathy existed. Prior to the events of 1821 he had not been admitted to the councils in state affairs, and his closest friends were among the young Portuguese officers, who, like most of their class, sympathised with the constitutional movement. Pedro was a Free Mason, and the Liberal opinions advocated in the lodges greatly influenced him. To Pedro, therefore,—young, ardent, popular, holding progressive notions,—both Brazilian and Portuguese Liberals naturally turned.

Seeing the rÔle of leader and ruler of Brazil ready to his hand, Pedro favoured the departure of his father for Portugal. A meeting of the Rio electors, held on the 21st of April, to elect members to the Cortes suddenly changed into a tumult, and demanded that the King assent to the Spanish Constitution before his departure. He had no choice but to yield, though probably neither he nor the popular leaders had ever read the document. The demonstrations continuing, Pedro became uneasy lest his father's journey should be delayed, and marched his troops into the square and cleared the people out at the point of the bayonet. This audacious move was followed by general stupefaction, and the King quietly escaped, leaving Pedro as regent. As his vessel weighed anchor he said to his son: "I fear Brazil before long will separate herself from Portugal; if so, rather than allow the crown to fall to some adventurer, place it on thy own head."

The grasping policy of the Portuguese members of the Cortes furnished the impulse that drove the Brazilians into union and independence. The Cortes met in Lisbon, and, although most of the Brazilian delegates had not arrived, immediately undertook to pass measures touching the most important interests of the younger kingdom. In December, 1821, news reached Brazil that decrees had been enacted requiring the prince to leave Brazil, abolishing the appeal courts at Rio, creating governors who were to supersede the juntas and be independent of local control, and sending garrisons to the principal cities. Tremendous popular excitement followed. The coupling of the order for Pedro's retirement with the provisions for the enslavement and disintegration of Brazil, made the provinces realise that he was the only centre around which they could rally for effective resistance. A cry rose up from the whole country, praying Pedro not to abandon them. The address sent by the provincial junta of SÃo Paulo was penned by the hand of JosÉ Bonifacio de Andrada, and may well be called the Brazilian declaration of independence.

JosÉ Bonifacio, whose voice and example, more than any other man's, gave expression and direction to the aspiration for independence, belonged to the English parliamentary school which was dominant then in liberal thought. The elevation of the young and progressive prince to an independent throne seemed an easy method of establishing constitutional government, as well as of securing Brazil's autonomy. Pedro did not hesitate long in acceding to the wish of the Brazilians. On January 9, 1822, he formally announced that he would remain in Brazil—thus defying the Portuguese Cortes. The word "independence" had not yet been employed, and there was a very general hope that the Portuguese would listen to reason when the Brazilian deputies arrived in Lisbon. The only active resistance to Pedro in Brazil came from the Portuguese soldiers, some of whom revolted and went so far as to march under arms to a point commanding the city of Rio, but their nerve failed them in face of the immense concourse of citizens who were preparing to fight.

Pedro threw himself unreservedly into the hands of the patriots. JosÉ Bonifacio was made Prime Minister, and measures taken to re-establish the control of the central over the provincial governments. But the ruling groups in the various capitals were not very ready to surrender their authority. Pedro called a council, but representatives from only four provinces responded. Bahia and Pernambuco were held in check by Portuguese garrisons, and other provinces hesitated before committing themselves. Meanwhile the Portuguese majority in the Cortes paid no attention to the warnings of the Brazilian members, but ruthlessly pushed forward the measures for the commercial and political subjection of Brazil. Most of the Brazilian members withdrew, while a squadron was sent to Rio to escort the prince back to Portugal. On May 13 1822, he assumed the title of "Perpetual Defender and Protector of Brazil," and from this to a formal declaration of independence was only a step. In June he notified the Cortes that Brazil must have her own legislative body, and, on his own responsibility, issued writs for a constituent assembly. The Cortes responded by re-enforcing the Bahia garrison, and the Bahianos retaliated by attacking the Portuguese troops. The Pernambucanos expelled their garrison and sent promises of adhesion to the prince. On the 7th of September Pedro was in SÃo Paulo, and there received despatches telling of still more violent measures taken by the Cortes, accompanied by letters from JosÉ Bonifacio urging that the opportunity they had so often planned for together had at last arrived. Pedro reflected but a moment, and then, dramatically drawing his sword, cried, "Independence or Death!" Everything had been carefully timed, and his entrance into Rio a few days later, wearing a cockade with the new device, was greeted with enthusiasm. On the 12th of October he was solemnly crowned "Constitutional Emperor of Brazil," announcing that he would accept the constitution to be drawn up by the approaching constituent assembly.

Prompt and efficient measures for the expulsion of the Portuguese garrisons from Bahia, MaranhÃo, ParÁ, and Montevideo were taken. The militia came forward enthusiastically; the regular forces were rapidly increased; Lord Cochrane, the celebrated free-lance English admiral, was placed in command of a fair-sized fleet which sailed at once for Bahia, and, defeating the ships which remained faithful to the Portuguese cause, established a blockade that soon enabled the land forces besieging the city to reduce the place. At MaranhÃo Cochrane's success was still easier; ParÁ also fell without resistance at the summons of one of his captains; and the news of these successes was followed by that of the surrender of the garrison at Montevideo. Within less than a year from the declaration of independence not a hostile Portuguese soldier remained on Brazilian soil.