The leaders of the self-styled "Glorious Revolution" were two colonels and a brigadier general, whose regime came to be known simply as "the junta," or "the colonels." Supporters of the coup were predominantly officers from lower-class backgrounds who had achieved status through career advancement in the armed forces. Fearful of losing their posts because of their involvement in right-wing conspiracies, they acted out of self-preservation, under the flimsy pretense of forestalling a communist takeover and defending Helleno-Christian civilization in general. The junta succeeded because of the political leadership vacuum at the time and because they were able to strike quickly and effectively. By seizing the main lines of communication, they presented an unsuspecting nation with a fait accompli.

Initially the colonels tried to rule through the king and the existing political system. But, gaining the cooperation of very few politicians, they soon began to arrest all those who showed signs of resisting the takeover, consolidating as much power as possible in their own hands. Andreas Papandreou, for example, was arrested for his connection to the Aspida group; he was released only under intense international pressure. As the methods of the colonels began to resemble those of the Metaxas dictatorship, Constantine organized a countercoup in December 1967 then fled into exile when his plan failed.

Colonel Georgios Papadopoulos, one of three officers who led the coup, rose to the top of the regime and remained there until November 1973. The junta's aims and policies were a curious mixture of populist reforms and paternalistic authoritarianism backed by propaganda and terror. The overarching, proclaimed intent of the military government was to purge Greek society of the moral sickness that had developed since the war. Their more frivolous social policies included the banning of miniskirts and the mandatory short hair for men. The regime lacked a base of popular support and remained in power through terror. A formidable secret police apparatus monitored society, using torture and committing other human rights violations that were widely reported by international organizations. In the first three years, the main targets of this policy were known supporters of the communists, but many centrist figures also were arrested.

The regime's brutality made it an international pariah. The only foreign dignitary of note to visit Greece during this period was the Greek-American United States vice president, Spiro Agnew. Greece withdrew from the EC in 1969 to avoid suspension of its association agreement. Nevertheless, Greece's NATO allies confined themselves to verbal condemnation because the regime fulfilled every geopolitical requirement, anchoring the alliance's defenses in the unstable eastern Mediterranean. The United States broke off full diplomatic relations only briefly after Constantine's exile; although military aid to Greece decreased between 1967 and 1973, in 1972 the United States negotiated permanent access to Greek port facilities for its Sixth Fleet.