Japanese forces landed and established beachheads near Gona and Buna on 21 July 1942. Opposed by Maroubra Force, then consisting of four platoons of the 39th Battalion and elements of the Papuan Infantry Battalion, they quickly advanced and captured Kokoda and its strategically vital airfield on 29 July. Despite reinforcement, the Australian forces were continually pushed back. The veteran Second Australian Imperial Force (AIF) 21st Brigade narrowly avoided capture in the Battle of Mission Ridge – Brigade Hill from 6 to 8 September. In the Battle of Ioribaiwa from 13 to 16 September, the 25th Brigade under Brigadier Kenneth Eather fought the Japanese to a halt but ceded the field to the Japanese, withdrawing to Imita Ridge.