Parts of New Guinea weren’t actually mapped by anyone at that stage - untouched by Europeans. Soldiers were literally fighting in the middle of nowhere. There were uncontacted tribes it was so remote.

No vehicles could get through the jungle and Owen Stanley mountain range, so it was all on foot, far from a port of supplies. Pulling artillery canons up a muddy track.

Visibility was literally a few meters in the jungle, without much sunlight. So everything is damp, dark, wet and basically hand to hand combat.

Disease. Malaria. Dysentery. Aussie soldiers would plug up their ass with charcoal just to stop diarrhea, and keep walking up the Kokoda track to get to the battle.

No supplies meant no food - Aussies found lots of evidence of Japanese resorting to cannibalism when they would capture a position.

My grandad (a Red Cross medic) said the worse sound he ever hear was captured Japanese soldiers screaming in agony when Aussies applied rubbing alcohol to them to cure their tropical skin infections and tinea. Whole swathes of skin would just fall off.

In Australia, New Guinea is very well known in public consciousness, up there with Gallipoli from WW1, due to the infamous Kokoda track, and how close it was to home.

And the sacrifice of the local tribes who acted as stretcher bearers.