During his first term, he applied a program of rapid industrialization, heavy investment on infrastructure and improvement on agricultural production, which led to the post-war Greek economic miracle.

In foreign affairs, he pursued an aggressive policy toward Greek membership in the European Economic Community (EEC), and abandoned the government's previous strategic goal for enosis (the unification of Greece and Cyprus) in favour of Cypriot independence.

During the Axis occupation, he spent his time between Athens and Serres, while in July 1944, he left to the Middle East to join the Greek government in exile.

His rise was strongly supported by fellow party-member and close friend Lambros Eftaxias, who served as Minister for Agriculture under the premiership of Konstantinos Tsaldaris.

One of the first bills he promoted as prime minister implemented the extension of full voting rights to women, which stood dormant although nominally approved in 1952.

In 1958, his government engaged in negotiations with the United Kingdom and Turkey, which culminated in the Zurich Agreement as a basis for a deal on the independence of Cyprus.

On 28 September 1960 German newspapers Hamburger Echo and Der Spiegel published excerpts of Merten's deposition to the German authorities where Merten claimed that Karamanlis, the then Minister for the Interior, Takos Makris and his wife, Doxoula (whom he described as Karamanlis's niece) along with then Deputy Minister of Defense Georgios Themelis were informers in Thessaloniki during the Nazi occupation of Greece.

Merten alleged that Karamanlis and Makris were rewarded for their services with a business in Thessaloniki which belonged to a Greek Jew sent to the Auschwitz concentration camp.

Karamanlis rejected the claims as unsubstantiated and absurd, and accused Merten of attempting to extort money from him prior to making the statements.

[9] He personally lobbied European leaders, such as Germany's Konrad Adenauer and France's Charles de Gaulle followed by two years of intense negotiations with Brussels.

The signing ceremony in Athens was attended by top government delegations from the six-member bloc of Germany, France, Italy, Belgium, Luxemburg and the Netherlands, a precursor of the European Union.

[12] Soon after returning to Greece during metapolitefsi Karamanlis reactivated his push for the country's full EEC membership in 1975 citing political and economic reasons.

[9][10] Karamanlis was convinced that Greece's membership in the EEC would ensure political stability in a nation having just undergone a transition from dictatorship to Democracy.

Greece became the tenth member of the EEC on 1 January 1981 three years earlier than the original protocol envisioned and despite the freezing of the treaty of accession during the junta (1967–1974).

[13] The elections were denounced by both main opposition parties, EDA and the Centre Union, who refused to recognise the result based on numerous cases of voter intimidation and irregularities, such as sudden massive increases in support for ERE against historical patterns, or the voting by deceased persons.

The Centre Union alleged that the election result had been staged by the shadowy "para-state" (παρακράτος) agents, including the army leadership, the Greek Central Intelligence Service, and the notoriously right-wing National Guard Defence Battalions, according to a prepared emergency plan code-named Pericles.

[14] Karamanlis's position was further undermined, and Papandreou's claims of an independently acting "para-state" given more credence, following the assassination of Grigoris Lambrakis, a leftist member of Parliament, by right-wing extremists during a pro-peace demonstration in Thessaloniki in May 1963, who were later revealed to have close links to the local gendarmerie.

Karamanlis opposed the trip, as he feared that it would provide the occasion for demonstrations against the political prisoners still held in Greece since the Civil War.

According to uncorroborated claims that were made by the former monarch only after both men had died, in 2006, Karamanlis replied to Bitsios that he would return under the condition that the King were to impose martial law, as was his constitutional prerogative.

In 2001, former agents of the Eastern German secret police, the Stasi, claimed to Greek investigative reporters that during the Cold War, they had orchestrated an operation of evidence falsification,[22][23] to present Karamanlis as having planned a coup and thus damage his reputation in an apparent disinformation propaganda campaign.

On 23 July 1974, President Phaedon Gizikis called a meeting of old guard politicians, including Panagiotis Kanellopoulos, Spiros Markezinis, Stephanos Stephanopoulos, Evangelos Averoff and others.

He insisted that Karamanlis was the only political personality who could lead a successful transition government, taking into consideration the new circumstances and dangers both inside and outside the country.

Throughout his stay in France, Karamanlis was a vocal opponent of the Regime of the Colonels, the military junta that seized power in Greece in April 1967.

During the inherently unstable first weeks of the metapolitefsi, Karamanlis was forced to sleep aboard a yacht watched over by a destroyer for fear of a new coup.

Two successive conferences in Geneva, where the Greek government was represented by George Mavros, failed to avert a full-scale invasion by Turkey on 14 August 1974 or the subsequent Turkish occupation of 37 percent of Cyprus.

His phrase became famous during the 1989 political crisis to characterize the state of affairs at the end of the second term of Papandreou: "Hellas has been transformed to an endless bedlam."

[31] Some of his left-wing opponents have accused him of condoning rightist "para-statal" groups, whose members undertook Via kai Notheia (Violence and Corruption), i.e., fraud during the electoral contests between ERE and Papandreou's Center Union party, and were responsible for the assassination of Gregoris Lambrakis.

Some of Karamanlis's conservative opponents have criticized his socialist economic policies during the 1970s, which included the nationalization of Olympic Airways and Emporiki Bank and the creation of a large public sector.

Karamanlis has also been criticized by Ange S. Vlachos for indecisiveness in his management of the Cyprus crisis in 1974[32] even though it is widely acknowledged that he skillfully avoided an all-out war with Turkey during that time.

On 29 June 2005 an audio-visual tribute celebrating Konstantinos Karamanlis's contribution to Greek culture took place at the Odeon of Herodes Atticus.