While Emperor Godaigo was exiled to Okinoshima Island, Masashige and Imperial Prince Morinaga, who fought with him in Yoshino in Yamato Province (present-day Nara Prefecture) and other places, held Kamiakasaka-jo Castle in Kawachi Province and Chihaya-jo Castle, which was a a castle built on a mountain to take advantage of the mountain's topography, built in the middle of Mt. Kongo (Kongo mountainous district), using guerrilla tactics, excrement attack and others, to fight against a huge army of the bakufu.
後醍醐が隠岐島に流罪となっている間にも、大和国（奈良県）の吉野などで戦った護良親王とともに、河内国の上赤坂城や金剛山(金剛山地)中腹に築いた山城、千早城に籠城してゲリラ戦法や糞尿攻撃などを駆使して幕府の大軍を相手に奮戦する。