In 1928, the Commander-in-Chief of the Asiatic Fleet, Admiral Frank B. Upham, was so impressed with the radio intelligence activities that he wanted to establish a radio intelligence center in his command. Specifically, he requested that an intercept unit complete with a decryption center be located in or near Manila Bay, with the mission of preventing surprise attack.

In October 1929, Joseph Goldstein and Truett Lusk, both graduates of "On-The-Roof Gang Class #1 under Harry Kidder, transferred from Station BAKER in Guam to the Philippines specifically to establish an intercept site at Olongapo near Subic Bay. After some frustrating delays, they began intercept duties in August 1932 as Station CAST. In early 1935, the intercept station was moved from Olongapo to Mariveles and then to Cavite Naval Base in 1936. Finally, in October 1939, the intercept station moved to a tunnel on the island of Corregidor called “Tunnel AFIRM.”

The intercept site at Corregidor was a significant improvement over Cavite from an operational perspective, since Cavite was susceptible to noise interference from the Navy Yard. Two months after this move, Station CAST was augmented with the mission and the personnel of Station ABLE, which was shut down because of the increasing aggression of Japan in Shanghai. Intercept Station CAST was secretly evacuated by submarine and abandoned in the early parts of 1942, after the Japanese had destroyed most of the U.S. assets on Corregidor and had taken over in the Philippines.