Why did war come to Papua New Guinea?

War came to Papua New Guinea because PNG stood in the way of Japanese domination over the south Pacific.

The defence of Port Moresby was critical to victory in the south Pacific and to the defence of Australia. Had Port Moresby fallen, it would have left northern Australia more vulnerable to attack.

Singapore had already fallen, Rabaul (PNG) had already fallen, and the Japanese troops were getting much closer. Over the period of a year or more, Darwin and northern parts of Australia experienced periodic bombings from the Japanese.

In May 1942, a Japanese invasion fleet departed Rabaul for Port Moresby, and the Battle of the Coral Sea began. It was a very real threat which was only turned back by the US aircraft leaving from carriers. After being turned back by the US, the Japanese then turned their attention to an attack over the Owen Stanley Range via the Kokoda Track, which linked the northern and southern coasts of Papua New Guinea. Thanks to the Papua New Guinean natives assisting the Australians and the US troops, the Japanese were turned back, having to retreat to bases at Buna, Gona and Sanananda, where they were eventually defeated.
War came to Papua New Guinea because PNG stood in the way of Japanese domination over the south Pacific.

The defence of Port Moresby was critical to victory in the south Pacific and to the defence of Australia. Had Port Moresby fallen, it would have left northern Australia more vulnerable to attack.

Singapore had already fallen, Rabaul (PNG) had already fallen, and the Japanese troops were getting much closer. Over the period of a year or more, Darwin and northern parts of Australia experienced periodic bombings from the Japanese.

In May 1942, a Japanese invasion fleet departed Rabaul for Port Moresby, and the Battle of the Coral Sea began. It was a very real threat which was only turned back by the US aircraft leaving from carriers. After being turned back by the US, the Japanese then turned their attention to an attack over the Owen Stanley Range via the Kokoda Track, which linked the northern and southern coasts of Papua New Guinea. Thanks to the Papua New Guinean natives assisting the Australians and the US troops, the Japanese were turned back, having to retreat to bases at Buna, Gona and Sanananda, where they were eventually defeated.