In 1274 during the Bunei War (the first attempted invasion by the Yuan Dynasty [Mongol]) of Genko (Mongol invasion attempt against Japan, consisting of two different wars) Suenaga joined the army of Kagesuke SHONI of Hakozaki, Hakata (present-day Fukuoka Prefecture), and had his corps based in Okinohama.
文永11年（1274年）、元(王朝)（蒙古）の第一次侵攻である文永の役（元寇）では、博多において箱崎の少弐景資の軍に参陣し、息浜に陣した。