Ezio Auditore da Firenze sent his Assassin recruits to Vienna to turn Maximilian against the Borgia in Rome. They knew Maximilian had taken a beating from Swiss mercenaries during his last war, and discovered they were working in the Papal Guard.
Shortly after, they found the mercenaries' leaders in a tavern, where they joined them and managed to poison their drinks after they had gotten them drunk, knocking them out. Following this, the recruits carried their victims to Maximilian, who was angered at first but had expected it. With this, he paid the Assassins well, and cut his funding to the Borgia while he investigated the incident.
The Swiss mercenary leaders were later employed as trainers by Maximilian, who also asked the Assassins to tutor his men. The Assassins accepted the offer, though they dressed up as condottieri to prevent anyone from discovering their real affiliation. Together with one of Maximilian's best knights, they trained the Landsknechte, and Maximilian promised them that they could call upon his best men if they ever needed them.