[2] Under his patronage, Ottone was appointed by Archbishop of Milan Leone da Perego as his envoy to France in 1252, gaining the trust of Pope Innocent IV, becoming his chaplain.

[4] The Pope's choice did not stop the hostility of Martino della Torre, who occupied Milan Cathedral on August 1262, resulting in his excommunication by the papal legate Filippo di Pistoia.

The two families were also politically opposed: the Della Torre were historically Guelphs and allied of Charles I of Anjou,[5] while the Visconti were Ghibellines and exponents of low nobility.

Still in Montefiascone, near Viterbo, where he received Pope's appointment, Ottone marched to Arona on 1 April 1263, where he met several nobles who had fled Milan owing to their opposition to Della Torre.

Ottone sought the support of his ally William VII, Marquess of Montferrat, who demanded the city's government as Capitano generale (general-captain), granted to him in 1278.

On May 1288, Matteo Visconti also gained the title of Imperial vicar by Rudolph I of Germany,[11] who thus avoided intervening directly in the Lombard political situation while still the nominal ruler of Milan.