Papua New Guinea and WWII turned the country in to a major theater in the battle for the Pacific with the Japanese forces landing first in Kavieng, New Ireland on the 21st January 1941 and soon after at Rabaul in New Britain, which they proceeded to turn into their main base along the South Pacific rim.
The Japanese launched their attack on Port Moresby in May 1942 from Rabaul, in the next stage of the grand plan for control of New Guinea together with the isolation and possible invasion of Australia to the south.
But in the Battle of the Coral Sea US carrier-based aircraft and the Australian Navy succeeding in forcing the Japanese armada back to its base in Rabaul.
In June 1942, after suffering devastating defeat at the Battle of Midway, the Japanese abandoned trying to take Port Moresby by naval attack and launched a surprise landing near Buna on the northeast coast of PNG, using it as a base from which to launch an overland advance across the Owen Stanley Range.
These mountains reach a height of 13,000 ft and are like a spine that runs down the Papuan peninsula creating a formidable, saw-toothed, jungle barrier that separates the northeast from the southwest of the country.
The defeat of this attack by the Australian Army on the Kokoda Track is one of the finest moments in the military history of Australia.