He was commonly known as Gen Daifu Hogan after his great-grandfather and joined the Genpei War as a commander of the Taira clan, achieving great feats including the defeat of Ishikawa-Genji (descendants of MINAMOTO no Yoshitoki, the younger brother of Yoshitada).
源大夫判官という曽祖父と同じ通称を名乗り、平家方の将として源平の合戦に参戦し、一族である石川源氏（義忠の弟の源義時の子孫）を討伐するなど活躍した。