The numbering of the legions is confusing, since several legions shared the same number with others. Augustus numbered the legions he founded himself from I, but also inherited numbers from his predecessors. Each emperor normally numbered the legions he raised himself starting from I. However, even this practice was not consistently followed. For example, Vespasian kept the same numbers as before for legions he raised from disbanded units. Trajan's first legion was numbered XXX because there were 29 other legions in existence at the time it was raised; but the second Trajanic legion was given the sequential number II. XVII, XVIII and XIX, the numbers of the legions annihilated in the Teutoburg Forest, were never used again. (These three legions are without titles, suggesting that in disgrace their titles may have been deliberately forgotten or left unmentioned.) As a result of this somewhat chaotic evolution, the legion's title became necessary to distinguish between legions with the same number.