Definition
The term "lower cannon" refers to the part of a suit of plate armor that protects the lower arm, specifically from the elbow to the wrist. It's often used interchangeably with "vambrace", although some sources may differentiate subtle design variations. Think of it as the lower half of a metal sleeve for your arm. The lower cannon's purpose was to deflect blows from weapons. Together with the upper cannon (or rerebrace) it provided full arm protection. Armor design was crucial for survival in medieval combat.