The high frequency direction finding (HFDF) fix in the above message was one of many prosecuted by dozens of U.S. Navy, British, and Canadian direction finding stations in the Atlantic periphery on the days following the President’s initiation of a naval blockade. Matthew M. Aid, in his book, The Secret Sentry, writes:
The two dozen or so U.S. Navy, British, and Canadian direction-finding stations ringing the Atlantic continuously monitored every radio transmission going to or from the twenty-two Soviet merchant ships approaching the Cuban quarantine line, in order to track the movements of the Russian ships… The U.S. Navy’s direction-finding stations began reporting to NSA that their tracking data indicated that some of the Russian merchant ships had stopped dead in the water, and that it seemed that at least eight of the ships had reversed course and were headed back toward Russia.
The value in such collection is not in the finding and fixing of the ships’ positions alone, but rather in the ability of such information to indicate that the ships had either stopped or reversed course. That is actionable intelligence. Such knowledge affords key leadership the time and the ability to make informed decisions. The message above, combined with many others like it, painted a clear picture of the Soviet’s intentions to not challenge the blockade in full force.
Such is one of the primary roles of a naval cryptologist — to find and fix the adversary. The fix part of this equation is primarily accomplished via direction finding. As demonstrated, direction finding provides specific actionable intelligence to warfighters on the ground, in the air, at sea, and on our networks. It contributes directly to providing Battlespace Awareness to the operational commander. Battlespace Awareness is, amongst other things, an understanding of when, where, and how our adversary operates. This understanding, combined with persistent surveillance, penetrating knowledge, and expertise within the electromagnetic spectrum provides the commander with time and “the target acquisition and targeting solutions necessary to apply force, both kinetic and non-kinetic.”
The Secret Sentry: The Untold Story of the National Security Agency, Matthew M. Aid (pp. 74-77)