Frederick IV of the Empty Pocket (1382 - 1446) was the Count of the Tyrol from 1406 until 1446. Frederick was the third son of the Habsburg Duke Leopold III. After his brother William died and his other brother Leopold was made the guardian of Archduke Albert V, Frederick was made the Count of the Tyrol and sole regent of Further Austria. The early years of his reign were marked by constant internal and external struggles. He had to overcome the resistance of the local nobility in 1406/7 who gave him the title "the Empty Pocket", repel a Bavarian invasion in 1410, and to deal with independence movements in Appenzell, which joined Switzerland as a protectorate in 1411.