The US was very successful. The US acquired MIG fighters and flew them in the Nevada testing grounds to find and exploit their weaknesses. They eventually had an entire squadron of them and they were used in training dogfights against fighter pilots who weren't expecting to see a real life MIG up close! The book Red Eagles is all about that unit. Most fighters came from countries that the Soviets were trying to woo, but had a regime change, were corrupt or broke, so the US would buy them from the country's leadership. The job was incredibly dangerous, the cockpit was laid out differently than American jets, the strange metric units were referred to as "kilometers per fortnight", and the maintainers had exactly zero experience or information on what to inspect and when since apparently the manuals didn't come with the jets. It's a pretty remarkable story and anyone who is interested in military aviation has to read the book.

There was also Project Azorian where the US saw very suspicious Soviet Navy active a thousand miles north of Hawaii. It looked like they were searching for something, well the US found out it was a nuclear sub that sank in 15,000 feet of water. Using the guise of a mining ship looking for minerals the Navy used a giant grappling claw to grab the sub and lift it to the surface where the claw broke. But they were able to study the nuclear power plant and other valuable documents.

When it came to old fashioned spying each side acquired important documents. Some major scores were the Russians had a mole in the Manhattan Project, the Americans got their hands on Soviet radar specs, I'll have to look through my bookshelf to see what book discusses these incidents but it's all pretty fascinating. Who needs James Bond novels when there's plenty of nonfiction accounts of doing equally impressive feats of espionage?