E ver since the Australians, who had advanced into the German lines near Fromelles on   July 19, 1916, retired to their own trenches next day after suffering unprecedented casualties, there has been debate about who was responsible for the debacle.
Some have blamed Maj-Gen. James McCay, the 51-year-old Australian general commanding the 5th  Australian Division, whose troops made the charge. He is not blameless.
 But in the course of writing my book, I have concluded it was McCay's superior, the British general Lt-Gen. Sir Richard Haking, commander of X1 Corps, who planned the attack, and his superiors including British commander-in-chief Gen. Sir Douglas Haig, who did not supervise him, who must take most of the blame. 
Haking's initial error was to recommend an operation which was a cross between an all-out advance, where surprise was an essential prerequisite for success, and a mere demonstration, designed to persuade the Germans they should not divert troops from the Fromelles front to the Somme battlefield further south.
In an attempt to kill Germans while achieving the latter aim, Haking instructed Australians  to repeatedly "show their bayonets over the parapet" prior to the attack.
 At the same time, "dummy heads and shoulders" were to be waved over the parapet, and officers were to "blow their whistles and shout orders" so that Germans would be tempted out of their trenches and shelled.
Unfortunately such measures meant the German defenders were waiting for the Australians when, at 6pm on   July 19, 1916, they attacked.
The Australians' plight was worsened because instead of bombarding the Germans with a heavy gun every 100 yards of trench attacked, which was generally accepted to be what was required, Haking recklessly decided that a heavy gun every 250 yards was sufficient.
The fact that some of the Australians were being asked by Haking to cross 400 yards of no-man's-land, disregarding GHQ's advice that 200 yards should be the maximum, reduced the chances of success further.
Although Australian troops  who crossed the narrower sector of no-man's-land on the left of the attack established a temporary bridgehead in the German lines, those in the 15th Australian Brigade on the right, who had 400 yards to negotiate, were cut down in their hundreds.
Haking's insistence that the attack on the main German strong point, known as the Sugar Loaf, should be made by a British brigade alongside and acting with the 15th Australian Brigade, coupled with Haking's failure to order that the two brigades had liaison officers in each other's headquarters, was a recipe for exacerbating the disaster.
 The communication deficit meant that the follow-up attack by the Australian 15th Brigade was made in the mistaken belief that the British on their right would be attacking simultaneously.
 In fact, unbeknown to the Australians, the planned British attack had been cancelled, and the Australians attacked alone. 
They were mown down like those who had gone before them.
Another critical mistake by Haking - for which McCay must share the blame - was his failure to insist that the Australians should leave men in the part of the German front line on the left which they did capture.
This would have stopped the enemy surrounding those Australians who advanced to the second German line.
Haking's refusal to allow McCay to order those Australians in the German lines to retire to the original Australian front line until the daylight hours of   July 20, even though Haking knew about midnight during the night of   July 19-20 that they were unsupported on their right flank, was another factor that increased Australian casualties unnecessarily.
 Haking's failure to insist that his order, explaining that the attack was only a demonstration to pin down the German troops, should not be carried into battle had disastrous consequences. 
The Germans found a copy of the order on the battlefield, possibly in the pocket of one of the Australian soldiers they captured.
Once the German commanders had read it, they realised they could move troops to the Somme as if the Fromelles attack had never happened.
 Hugh Sebag-Montefiore's Somme: Into The Breach is published by Viking Penguin, RRP $35