Japan routinely moved major formations around China and Manchuria and had recently fought the Soviet Union on the border. Additional troop and landing-ship movements could therefore blend into an existing pattern more easily than a sudden concentration of carriers. American observers were especially focused on the location of Japanese battleships and carrier forces. Deception could exploit an opponent's collection priorities even when the underlying movement was large.
Notable Point · 2:30:35-2:31:37
Why troop movements could hide inside Japan's existing wars
Large Japanese troop movements around China and Manchuria were less conspicuous than carrier movements, while American attention remained fixed on the location of major warships.