on 9 january, japanese forces under lt. gen. susumu morioka attacked the eastern side of the abucay-mauban line. they were beaten by the u.s. the japanese advanced to the salian river valley. u.s. troops fought off the attackers. at another battle to the west, a japanese force got past the abucay-mauban line. the u.s. stopped their advance. on 15 january, 1st regular division was bombed, but they held the line. the japanese moved through a gap. the abucay-mauban line had to be abandoned on 22 january.