After the fall of Lae, the 9th Division was given the task of capturing the Huon Peninsula. The 20th Brigade landed near the strategic harbour of Finschhafen on 22 September 1943, and secured the area. The Japanese responded by dispatching the 20th Division overland to the area and the remainder of the 9th Division was gradually brought in to reinforce the 20th Brigade against the expected counter-attack. The Japanese mounted a strong attack in mid-October which was defeated by the 9th Division after heavy fighting. During the second half of November the 9th Division captured the hills inland of Finschhafen from well dug in Japanese forces. Following its defeat the 20th Division retreated along the coast with the 9th Division and 4th Brigade in pursuit. The Allies scored a major intelligence victory towards the end of this campaign when Australian engineers found the 20th Division's entire cipher library, which had been buried by the retreating Japanese. These documents led to a code breaking breakthrough which enabled MacArthur to accelerate the Allied advance by bypassing Japanese defences.