It is not, however, difficult to reconstruct the course of events.  On the nights of the twelfth and thirteenth of October, soon after Claudius had been suddenly stricken down by his violent malady, the doctors announced to Agrippina that the emperor was lost.  Agrippina immediately understood that since the family of Augustus could at that moment present no full-grown man as candidate for the imperial office, there was grave danger that the senate might refuse to confer the supreme power either upon Nero or Britannicus.  The only means of avoiding this danger was to bring pressure to bear upon the senate through the pretorian cohorts, which were as friendly to the family of Augustus as the senate was hostile.  She must present one of the two youths to the guards and have him acclaimed not head of the empire, but head of the armies.  The senate would thereby be constrained to proclaim him head of the empire, as they had done in the case of Claudius.

But which one of the two youths was it best to choose, Claudius’s son by blood or his son by adoption?  Nero was chosen as the result of the unrighteous ambition of Agrippina, so Tacitus says.  It is very probable that Agrippina was more eager to see her own son at the head of the empire than to see Britannicus there; but this does not seem to have been the real reason of her choice, for it could not have been otherwise, even if Agrippina had detested Nero and had cherished Britannicus with a maternal affection.  Nero was four years older than Britannicus, and therefore he had to be given the preference over the latter.  It was a very bold move to propose that the senate make a youth of seventeen emperor; it would have been nothing less than folly to ask that they accept a thirteen-year-old lad as commander-in-chief of the imperial armies of Rome.

Through the help of Seneca and Burrhus, the plan developed by Agrippina was carried out with rapidity and success.  On the thirteenth of October, after matters had been arranged with the troops, the doors of the imperial palace were thrown open at noon; Nero, accompanied by Burrhus, advanced to the cohort which was on guard.  He was received with joyous welcome, placed in a litter, borne to the quarters of the pretorians, and acclaimed head of the army.  The senate grudgingly confirmed his election.  There resulted in Rome a most extraordinary situation:  a youth of seventeen, educated in the antique manner, and, though already married, still entirely under the tutelage of a strict mother, had been elevated to the highest position in the immense empire.  He was ignorant of the luxury, pleasure, and elegance which were becoming general in the great families; outside of a lively disposition and docility toward his mother, he had up to this point shown no special quality, and no particular vice.  Only one peculiarity had been noticed in him:  he had studied with great zest music, painting, sculpture, and poetry, and had made himself proficient in these arts, which were considered frivolous and useless for a Roman noble.  On the contrary, he had neglected oratory, which was held a necessary art by an aristocracy like the Roman, whose duty it was to use speech at councils, in the tribunals, and in the senate, just as it used the sword on the fields of battle.  But the majority believed that this was merely a passing caprice of youth.