His government was marked by the beginning of political openness and a softening of the repression imposed by the military dictatorship, but he faced strong opposition from hardline politicians.

Significant events during his tenure included the merger of Guanabara with Rio de Janeiro, the division of Mato Grosso with the creation of Mato Grosso do Sul, the resumption of diplomatic relations with the People's Republic of China, recognition of Angola's independence, the signing of nuclear agreements with West Germany, the initiation of Brazil's democratization process, the repeal of AI-5, and significant progress in the construction of the Itaipu Hydroelectric Plant.

Geisel witnessed and participated in the most prominent events of Brazilian history in the 20th century, such as the Revolution of 1930, the Getúlio Vargas dictatorship of Estado Novo and its overthrow in 1945.

Geisel was an important figure during the coup and became Chief of the Military Staff of President Humberto de Alencar Castelo Branco from 1964 until 1967.

For the first time during the era of military rule, the Brazilian Democratic Movement (MDB) actually put up a candidate in the person of longtime deputy Ulysses Guimarães.

The expectation was that the combined effects of import substitution industrialization and export expansion eventually would bring about growing trade surpluses, allowing the service and repayment of the foreign debt.

[citation needed] President Geisel sought to maintain high economic growth rates, while dealing with the effects of the 1973 oil crisis.

Together with his Chief of Staff, Minister Golbery do Couto e Silva Geisel devised a plan of gradual, slow democratization that would eventually succeed despite all the threats and opposition from hard-liners.

He replaced several regional commanders with trusted officers and labeled his political program abertura and distensão, meaning a gradual relaxation of authoritarian rule.

In late December 1978 he announced the end of the authoritarian Institutional Act 5, allowed exiled citizens to return, restored habeas corpus and full political rights, repealed the extraordinary powers of the president, and planned the indirect election of General João Figueiredo as his successor.

In 2018, an unearthed CIA memorandum from 11 April 1974 sent by William Colby to U.S. Secretary of State Henry Kissinger details the summary executions of over 100 "subversives" which were personally authorized by Ernesto Geisel himself.

Brazil established diplomatic relations with the People's Republic of China and socialist-led governments of Angola and Mozambique, signaling a growing distance between Brasília and Washington.

Although both countries remained allies, Geisel was keen to seek new alliances and, more importantly, new economic opportunities in other parts of the world, especially Africa and Asia.

Because Brazil was 80% dependent on imported oil, Geisel shifted the country from a critical support of Israel to a more neutral stance on Middle Eastern affairs.

The 1975 agreement with West Germany to build nuclear reactors produced confrontation with the Carter administration, which also scolded the Geisel government for abusing human rights.