Was the Battle of Cannae a roman tactical error or the ultimate sign of Hannibal's military genius?

Question

The roman general Terantius Varro could have used his reservs (principes or triarii) to protect the rear from the numidian cavalry assault rather than engaging them into that dreadful, full scale frontal atack on Hannibal's infantry.

Answer 1

Indeed He could, but in historical battles, the fate of tho8usands very often rested on the shoulders of one or two men. The romans at this point(and indeed before and for a time after) were the most sophisticated war machine that the world had seen. Rome frequently went to war against numerically superior forces, and more than often won through, with the use of superior tactics, weaponry, etc.
What many forces such as this suffer from, is an arrogance in themselves and their abilities, and these leaders often underestimate their enemies - with the disastrous consequencies.
The leader varro, decided that there would be no definite plan, and that he wouls simply use his own numerical superiority, and the better training and equipment of his legionaries to win through. He had the numerical superiority, and yet he did not exploit this, all his forces were concentrated - making it easier for hannibal.
What hannibal did, was to load his flanks with light troops, and he oredered then ti give way slightly to the advancing romans. What then happened was a crescent shape in the form of hannibals line, as the romas ploughed - effectively doin hannibals work for him, and helpint to encircle themselves.
Couple that with the ineffective use of the roman cavalry, and the caarthaginian horse, then returning to help massacre the surrounded romams it is little wonder, that the slaughter was so high in numbers.
Rome learned many lessond from this blunder. - Little consolation, to the thousands of dead legionaries.
A roman leaders arrogance, and underestimation, and a brilliant leader, with the intelligence to recognise an opportunity when they saw one.

Answer 2

The Roman army defeated itself, committing to one tactic or strategy without improvising to meet Hannibals cavalry threats to their flanks. One could say, Hannibal used his leadership to lure the central Roman legions forward, but, in the end, Varro did not take the initiative to change in the face of changing tactics.

Answer 3

The latter. Hannibal knew of Varro's impatience to do battle & did not have a cool head to appraise the situations.

Also, Hannibal had instructed his centre to fall back in relation to the wings, creating a false impression to the Romans that the Carthaginians were retreating, enticing them to rush headlong to chase the "retreating enemy", so much so that they left their flanks & rear unguarded.