Factual error: Mel Gibson sits around the campfire at the railway camp with the lads, reading newspaper reports of the April 25, 1915 landing at Gallipoli. The 3rd Light Horse Brigade (including the 10th Light Horse Regiment from Western Australia) landed at Gallipoli on 20 May 1915. This would have given him less than 3 weeks to enlist, train, travel to Egypt by ship and land on the Peninsula. A bit of a stretch. In reality, the 10 Light Horse regiment was raised in October 1914, with the 1st-3rd reinforcements departing Fremantle February 19-22, 1915.
Factual error: Mel Gibson and Mark Lee leave their jobs working on the Pichi Richi Railway (north of Adelaide) to join the Australian Light Horse Brigade (about to sail to Turkey from Perth in 1914). To do this, we see them travel over 1000 miles across the Nullarbor Plain by train. But the tracks were not laid until 1927.