And your feet shod with the preparation of the gospel of peace;
Note 13 at Eph 6:15: Paul drew this metaphor from the Roman military soldier. Roman warriors, as well as Greek ones, would wear sandals with very thick soles that were fastened to the feet by leather thongs. The Roman soldier's shoes had thickly studded nails, or cleats. One historian said the reason that Julius Caesar was such a success as a general was because his men wore military shoes that made it possible to cover long distances in short periods of time.
These military shoes, which are similar to football cleats, not only allowed soldiers rapid movement but also gave them stability in hand-to-hand combat. In the spiritual realm, the shoes of the Gospel of peace make a messenger prepared to share the glad tidings of peace. The Living Bible describes this as "shoes that are able to speed you on as you preach the Good News of peace." The New International Version translates this as "your feet fitted with the readiness that comes from the gospel of peace."
Isa 52:7 describes these shoes similarly: "How beautiful upon the mountains are the feet of him that bringeth good tidings, that publisheth peace; that bringeth good tidings of good, that publisheth salvation."
The Gospel of peace being spoken of here is not peace among mankind; that is a byproduct. Rather, this is speaking of peace between God and mankind. Understanding that God is no longer mad at us keeps us going (see note 2 at Ro 5:1).