Japan collected strong naval force in the Truk area according to the U.S. Joint Intelligence Committee. Daily summary dated 19 January 1942

An item reported that the Japanese naval strength in the Truk area was probably consisting of 2 battleships, 2 heavy cruisers, 4 light cruisers, 5 aircraft carriers, 12 destroyers, 9 submarines, 2 seaplane tenders, many naval auxilairies and numerous merchant troop transports or supply ships. The J.I.C. commented that she expected an offensive to the south.

Source

Map Room Papers (Roosevelt Administration), 1942 - 1945. U.S. Joint Intelligence Committee. Daily summary dated 19 January 1942 No. 40