In The Siege of Macindaw, he did not like the idea of being commanded by Horace, whom he called a boy, still wet behind the ears. Horace fought him and broke his nose, gaining his respect in the process and Nils came to be Horace's most fervent supporter. Nils fought in the battle at Macindaw as well.
In The Emperor of Nihon-Ja, he participated in a battle against pirates. He almost went after the pirates single-handedly before being commanded to return to The Wolfwill by Gundar who sees Nils is getting carried away.