Complex sentence: The crossing began at 03:00 hours on 1 April, and the three battalions undertaking the crossing made heavy work of it and when they were halfway across the two forward battalions were spotted by the Australians in the moonlight and engaged with machine gun and rifle fire.
Split into simpler sentences: The crossing began at 03:00 hours on 1 April, and the three battalions undertaking the crossing made heavy work of it. When they were halfway across the two forward battalions were spotted by the Australians in the moonlight and engaged with machine gun and rifle fire.