The Second AIF were involved in the battle for the Kokoda Trail (not track), in New Guinea. At first, the defence of the track was in the hands of several militia (non-regular army troops, like the Reserve these days) units. They moved from Port Moresby in the south, overland northwards along the Kokoda Track. Around this time, quite enormous and seasoned Japanese South Seas Forces troops were landing in the northern side, and marching south - they did this on the assumption that no one would expect a land assault across New Guinea because the track was thought not to be able to support an army. Macarthur (US General also commanding the Australian forces at this time) also thought the track would not sustain an army, which is why he only sent militia. The militia units suffered heavily from the conditions, braving horrible mud, rain, humidity, and the problems that come with jungle life including wounds that will not heal, and dysentery from poor food supplies. They advanced as far north as Kokoda (a small plateau on the top of the Owen Stanley Range) before deciding this was a fit place to fight. The Japanese then encountered a well dug-in bunch of quite untrained troops. The re-supplies that were meant to come to the troops did not appear, and they found themslevs running short of ammunition and food - they had marched beyond the realistic capacity of the supply units to get supplies through to them. The militia fought valiantly and repulsed the Japanese many times before finally having to evacuate their positions - outnumbered ten to one it is suprising they lasted in Kokoda as long as they did. There was essentially a long running battle with the Japanese all the way back down the track towards Port Moresby - for several months the Australian units would stand and fight, then melt way into the jungle to find another place to fight. Each time, the Japanese suffered a huge numbers of casualties, espcially compared to the Australians. From this point onwards the Japanese were getting farther from their supply points in the north, while the Australians were getting closer to their supply points in the south. The Japanese started suffering what the Australians had in Kokoda as their supply lines grew too long and difficult - low food, low ammunition. 2nd AIF units, returned from fighting in the Middle East, started to arrive to bolster the militia units and replace them. So the fighting became even tougher for the Japanese at a time they could least afford it. They crumbled within sight of Port Moresby and melted back up the track to the north, with Australian militia in hot pursuit.