 Complete the following phrase:  On 31 March, that group was dissolved, and Threadfin received orders to join and near Bungo Suido, the primary entrance to the Seto Inland Sea which separates Honshū from Kyūshū and Shikoku. The new attack groups primary assignment was to guard against an undetected sortie of the remainder of Japans fleet during the Allied assault on Okinawa. On the evening of 6 April, Threadfin made radar contact with what later proved to be an 