Translate, “Having shod your feet” (referring to the sandals, or to the military shoes then used).
the preparation - rather, “the preparedness,” or “readiness of,” that is, arising from the “Gospel” (Psa 10:17). Preparedness to do and suffer all that God wills; readiness for march, as a Christian soldier.
gospel of peace - (compare Luk 1:79; Rom 10:15). The “peace” within forms a beautiful contrast to the raging of the outward conflict (Isa 26:3; Phi 4:7).