Gordon Corera for the BBC takes on the interesting question of how valuable Cold War intelligence activities really were:
One reason it is hard to make a judgement is that much of the intelligence collected was military or tactical in nature, and would only have proven useful if the Cold War had gone hot.
Much effort was expended in stealing secrets like the Soviet order of battle or the design of new Soviet tanks which would have been invaluable in case of war.
This type of intelligence was collected by electronic means and satellite reconnaissance, as well as by human spies. It was used to work out how to best equip and prepare the military.
How invaluable would tactical intelligence on Soviet tanks have really been? It seems to me that the world—and certainly Britain—would be burned to a crisp one way or another. Who cares if our tanks beat their tanks prompting them to launch a nuclear first strike rather than their tanks beating our tanks prompting us to launch a nuclear first strike? There’s actually something rather astounding about the huge quantity of conventional armed forces that both sides built up on the European continent. Dwight Eisenhower, as I recall, was against this and thought that a modest-sized conventional force paired with the strategic nuclear deterrent would be good enough.
He later indicates that some valuable political intelligence was gathering regarding the Kremlin’s thinking that eventually convinced Reagan and Thatcher that the Russians were genuinely concerned that the West’s hawkish new leaders would launch an unprovoked attack. This, in turn, got the U.S. and U.K. to try to be more reassuring and generally calmed things down.