 At the end of 1536, he was imprisoned along with Medeghino in the Castello Sforzesco of Milan as he was suspected of being an accomplice to the rebel Lodovico da Birago.After that he offered his services to the Holy Roman Empire and fought in Hungary.With 300 infantrymen at his command, in 1542 Serbelloni distinguished himself against the Ottoman Turks in the defence of Esztergom.