What is the name of the SciFi book where a machine was invented that allows people using it to view into the past? I believe it used Tachyons or neutrons that would pass through matter, so it could view through solid rock, walls etc. Initially used to record war battle scenes that were sold to movies to generate capital to improve the machine, it was later discovered to allow viewing almost real-time anywhere causing complete lack of privacy for everyone. I thought it was Macroscope but after I found a copy it was a different story. I read it probably in the 60's or 70's.
Asimov's "The Dead Past" (mostly) fits your description:
Tachyons or neutrons (check): The chronoscope uses "neutrinics" as the basis of time viewing. In the story, neutrinos move both through space and time, and can be focused to observe the past.
Battle scenes (not quite): The protagonist wants to use the chronoscope to research ancient Carthage.
Lack of privacy (check): Quoting the story, "If you focus the chronoscope in the past of one-hundredth of a second ago? Aren't you watching the present?"
It's probably E for Effort, a 1947 novelette by T. L. Sherred.
Taking place at some time in the near future (relative to when it was written), the story is briefly framed as a manuscript delivered to a civilian by the military under circumstances of great tension.
The manuscript is a long letter to "Joe", apparently a bartender, by Ed Lefko. He describes seeing a silent but color movie aimed at Mexican-Americans in a run-down theater in Detroit. The movie recounts Cortés's conquest of Mexico with remarkably realistic sets and acting and a huge cast. The projectionist, a World War II veteran named Miguel "Mike" Laviada, tells Ed that he made the movie using a time viewer he invented, which he demonstrates. However, Mike has not been able to raise the capital needed to shoot the picture on high-quality film, add sound and other improvements, and get it distributed and advertised. He and Ed become partners, and at Ed's suggestion, they raise money by using the machine to blackmail wealthy people.
They spend a year making most of a new film out of time-viewed footage of Alexander the Great. They take it to Hollywood, where the high quality of the film easily convinces a producer and his associates to finish it, including using actors for scenes that appear in Alexander's biographies but did not really happen, and market it. The film is a great success with critics and viewers.
Ed and Mike admit the machine's existence to their associates and persuade them to join in their plan to expose the corruption of many famous people involved in the wars. The film causes riots in many countries and greatly increases international hostility.
The Light of Other Days by Arthur C Clarke
"The wormhole technology is first used to send digital information via gamma rays, then developed further to transmit light waves. The media corporation that develops this advance can spy on anyone anywhere it chooses.
When the technology is released to the general public, it effectively destroys all secrecy and privacy"