During the cold war there was a rising fear the Soviets were getting way ahead of us, enough so a buildup of our forces was considered, even with some pro-active action in mind. Around then they tapped secret undersea communication cables and found they weren't as dangerous as the previous intel had suggested, thus averting some nastyness.

What I found amusing about the story was how they found the cables. They knew there were undersea communication cables but didn't know where. But one of the people in charge remembered growing up in a costal area where there was an undersea cable. He recalled a big warning sign where the cable went into the water. He had "Warning, Undersea Cable" translated into Russian and had a sub go looking for the sign and sure enough found it.