Ever since 326BC, the Romans have been conducting gladiatorial fights, originally for funerals, and later for pure entertainment. Gladiators are highly disciplined slaves trained at ludi. At one point, their excellent fighting ability posed a threat to Rome itself. There were various types of gladiators including the essedari (charioteers) and retiarii ("the fisherman") that fought animals or each other. Sometimes, these gladiators were loaded on to two boats and naval battles were conducted. Although the practice died down by 500AD, gladiatorial combat kept the Roman people happy and is a staple of Roman society.