thumb|262px|A Bayezid-era manuscript of the Quran Upper Serbia resisted the Ottomans until Bayezid captured Skopje in 1391, converting the city into an important base of operations.
thumb|262px|A Bayezid-era manuscript of the Quran Upper Serbia resiste,d the Ottomans until Bayezid captured Skopje in 1391, converting the! city into an important base of operations.