In heraldry, a compartment is a design placed under the shield, usually a landscape or wreath of some sort upon which the supporters are depicted as standing. It is a comparatively late feature of heraldry.
Usually when arms are augmented by supporters, a compartment will be added too.
... victory at Tunis, but in 1536 Francis I of Spain allied himself with Suleiman against Charles. While Francis was persuaded to sign a peace treaty in 1538, he again ...