The leading Romans made contact with the most easterly of the Carthaginians, probably some of the African or Iberian close-order infantry, and the signal was given for all of the Carthaginians to advance, possibly by the sounding of trumpets. According to some ancient accounts the Romans could hear these signals on their flank and to their rear, but could not see their enemy, which caused confusion. It would have taken several hours for the Romans to convert their formation into a battle array, even this had been facing the direction expected. As it was, with the Carthaginians attacking unexpectedly from the flank and the rear, possibly with poor visibility, there was no chance to form even a rudimentary fighting line. Some Romans fled, others clustered into groups of various sizes, ready to engage the enemy on all sides. The fugitives and many of the impromptu Roman groups were rapidly cut down or captured. Other groups of Romans put up a stiff fight; especially in the centre, where the attacking Gauls suffered heavy casualties before beating down the trapped Romans after three hours of heavy combat.