I agree with what seleucids said except for the part about the Romans. The Romans did in fact lose many battles to the Celts and Celtiberians, probably a main reason why they decided to adapt their styles of weapons and armor. The Romans were master imitators; they did the same with their formations after engaging and being defeated by the Samnites on multiple occasions. Before Telamon and still to a lesser degree afterward, the Romans were terrified of the Gauls partly because their city had been sacked by migrating Celts. And we all know that the Celtiberian Wars were some of the bloodiest and most hotly contested conflicts that Rome ever involved themselves in. They were supposedly highly controversial in the eternal city itself at the time because of their great cost in money and lives.