The Pre-Dragnet Cold War Contact Chaining

I’m still working through some things from Judge Richard Leon’s injunction against the phone dragnet.

But for the moment I wanted to point to something the government claimed in the FBI’s declaration in the case, by Acting Assistant Director Robert Holley. He says,

For decades reaching back to the Cold-War era, the FBI has relied on contact chaining as a method of detecting foreign espionage networks and operatives, both in the United States and abroad, and disrupting their plans.

The language here seems somewhat forced. “Decades reaching back to the Cold War-era” might only mean 1988.

Moreover, the fact that FBI claims they’ve been doing this for “decades” suggests they’ve been doing it for decades before they put together the phone dragnet, even decades before they required telecoms to keep phone records for 18 months.

Doesn’t that mean it’s possible to do successfully without the dragnet and without 5 years of data?

If the technique, absent the dragnet, was effective against the Soviet Union, why do we need a dragnet against a less powerful adversary now?