“Millions of private telegrams sent from, to, or through the United States were obtained by the National Security Agency from 1947 to 1975 under a secret arrangement with three United States telegraph companies.”

— Senate Select Committee to Study Government Operations With Respect

to Intelligence Activities, 1976

Yes, America, we have been here before.

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Government surveillance of Americans, in the name of protecting the nation, didn’t start with the National Security Agency’s recently revealed collection of citizens’ telephone records.

Nearly 40 years ago, a year-long investigation by a Senate committee chaired by Frank Church (D-Idaho) uncovered a history of U.S. intelligence agencies scrutinizing Americans engaged in lawful activities. The snooping was both vast and shocking.

From the Church Committee report:

●“Nearly a quarter of a million first class letters were opened and photographed in the United States by the CIA between 1953-1973, producing a CIA computerized index of nearly one and one-half million names.

●“At least 130,000 first class letters were opened and photographed by the FBI between 1940-1966 in eight U.S. cities.

●“Some 300,000 individuals were indexed in a CIA computer system and separate files were created on approximately 7,200 Americans and over 100 domestic groups during the course of CIA’s Operation CHAOS (1967-1973).

●“An estimated 100,000 Americans were the subjects of United States Army intelligence files created between the mid-1960’s and 1971.

●“Intelligence files on more than 11,000 individuals and groups were created by the Internal Revenue Service between 1969 and 1973 and tax investigations were started on the basis of political rather than tax criteria.”

Yes, history does repeat itself, and sometimes for the same reasons.

Back then, the Cold War and fear of foreign subversion prompted our federal government to surveil U.S. citizens.

Then, the threat was communism. Now, it’s terrorism.

The need to detect terrorist plots is the government justification for collecting the metadata of Americans’ phone calls.

But the information being amassed is not just a record of phone calls, callers’ location and lengths of conversations. The government is also collecting millions of contact lists from e-mail and instant-messaging accounts around the world, The Post reported last fall.

Spying used to take place by secretly opening postal mail. Now, government surveillance is conducted by sophisticated electronics.

If anything has changed over the years, it is not just the methods by which people communicate but also the government’s technical capacity to collect information. Its willingness has been there all along.

And along the way, when there is public furor over intelligence excesses — as happened after the release of the Church report — note that the government’s powers seem to broaden.

Witness the USA Patriot Act, which Congress passed by overwhelming, bipartisan margins after the Sept. 11, 2001, attacks. The law gave the government new tools to detect and prevent terrorism, including sweeping surveillance powers.

This is not to say foreign threats aren’t real.

Cold War spy rings were not figments of the imagination. And American spies did send secrets to the Soviets. FBI agent Robert Hanssen was a spy for Russia. So, too, the CIA’s Aldrich H. Ames, who compromised a trove of U.S. assets.

Likewise, the 9/11 attacks and the 1993 World Trade Center bombing were horrors planned, financed and executed by foreign terrorists. “Shoe bomber” Richard Reid and “underwear bomber” Umar Farouk Abdulmutallab weren’t lone wolves: Both were trained by terrorists and furnished with instruments of destruction.

Intelligence collection, pursued aggressively, is a legitimate response to detect and quash such threats.

But tensions remain between protecting Americans and defending the civil liberties enshrined in the Bill of Rights.

The mistake is to see this struggle as a Democratic or Republican problem.

Administrations of both parties have embraced measures and investigative techniques to fend off foreign assaults on the home front.

The challenge is not to let well-founded fears blind us to a potential infringement upon constitutionally guaranteed civil liberties.

Freedom from unreasonable searches and the freedoms of speech and association should still count for something.

At issue today, as in the past: Who or what can impose restraint on government power that threatens its own citizens? Can the executive branch be counted upon to check itself? The Founders answered that question with their system of checks and balances.

When the system tilts, lopsided, agencies go unsupervised, telegrams are read, letters opened, cellphone calls collected — and government, uncontrolled and unaccountable, goes where it doesn’t belong.

Are Congress and the courts listening? Is one or are both complicit?

Read more from Colbert King’s archive.