Two words describe the bond between the Kamakura shogun and his vassals. Go’on, favor, is what the shogun gave his vassals, the gokenin: appointment to posts, new land, and confirmation of the land they already held. Hōkō, service, is what the vassals gave back: fighting in war, guard duty in peace, and payments.
A vassal who neglected his service could lose the land he had received.