When Musa became self-proclaimed sultan in European part of the Ottoman Empire, he attacked Serbia in early 1412 but was defeated by Stefan near Novo Brdo in Kosovo.
Kui Musa end ise Osmanite riigi Euroopa-osa sultaniks kuulutas, ründas ta 1412. aasta alguses Serbiat, kuid sai Stefani käest Novo Brdo juures Kosovos lüüa.