… a body of people, typically influential members of government agencies or the military, believed to be involved in the secret manipulation or control of government policy:  “The deep state and its policy of allowing extremist ideologies to flourish may be the actual issues of concern.”

According to an American political conspiracy theory, the deep state is a clandestine network of members of the federal government (especially within the FBI and CIA), working in conjunction with high-level financial and industrial entities and leaders, to exercise power alongside or within the elected United States government. The term deep state originated in the 1990’s as a reference to an alleged longtime deep state in Turkey but began to be used to refer to the American government as well, including during the Obama administration.  However, the theory reached mainstream recognition under the presidency of Donald Trump, who referenced an alleged “deep state” working against him and his administration’s agenda. 

The use of Trump’s Twitter account, combined with other elements of right-wing populist movements during his presidency, gave birth to numerous conspiracy theory groups, such as QAnon. The term has precedents since at least the 1950s, including the concept of the military–industrial complex, which posits a cabal of generals and defense contractors who enrich themselves through pushing the country into endless wars.