I have argued before that I believe few organizations did as much to prevent the Cold War turning into a hot one than the various intelligence agencies, CIA and KGB among them.   The reason for this is that each side lacked accurate knowledge of the true beliefs and intentions of the other side, and the intelligence agencies were at the forefront of identifying, calibrating and verifying those beliefs and intentions.
A good example was the series of NATO military exercises in 1983 which the USSR erroneously feared would be a cover for a pre-emptive nuclear strike against them.   To preclude that possibility, the Soviet leadership came very close to launching their own pre-emptive nuclear strike.  New evidence has come to light about the mis-understandings that each side had about the other, as reported here:

A classified British Joint Intelligence Committee (JIC) report written shortly afterwards recorded the observation from one official that “we cannot discount the possibility that at least some Soviet officials/officers may have misinterpreted Able Archer 83 and possibly other nuclear CPXs [command post exercises] as posing a real threat.”   The cabinet secretary at the time, Sir Robert Armstrong, briefed Thatcher that the Soviets’ response did not appear to be an exercise because it “took place over a major Soviet holiday, it had the form of actual military activity and alerts, not just war-gaming, and it was limited geographically to the area, central Europe, covered by the Nato exercise which the Soviet Union was monitoring”.
Armstrong told Thatcher that Moscow’s response “shows the concern of the Soviet Union over a possible Nato surprise attack mounted under cover of exercises”. Much of the intelligence for the briefings to Thatcher, suggesting some in the Kremlin believed that the Able Archer exercise posed a “real threat”, came from the Soviet defector Oleg Gordievsky.
Formerly classified files reveal Thatcher was so alarmed by the briefings that she ordered her officials to “consider what could be done to remove the danger that, by miscalculating western intentions, the Soviet Union would over-react”. She ordered her officials to “urgently consider how to approach the Americans on the question of possible Soviet misapprehensions about a surprise Nato attack”.
Formerly secret documents reveal that, in response, the Foreign Office and Ministry of Defence drafted a joint paper for discussion with the US that proposed “Nato should inform the Soviet Union on a routine basis of proposed Nato exercise activity involving nuclear play”.

I wonder if the UK Government communicated anything to the Soviets about the exercises not being a cover for a surprise attack.   And, if so, was their message believed?  Of course, as I’ve discussed before, merely telling your enemy something does not mean that they will believe that something, and nor should it.  And this is why Governments need subtle, strategic analysis of intelligence, not merely the raw data.  The case of Yuri Nosenko is a good example where what the other side believes you believe has consequences, and these consequences need to be considered when deciding what to believe.  And for this reason, clever espionage agencies try to ensure the existence of channels of communication to the enemy which the enemy trusts, so that messages sent through the channel are likely to be believed.   Perhaps, for example, British intelligence knew that Kim Philby and his Cambridge colleagues were Soviet agents many years before they fled to the USSR.