The six horses which pull the caisson through the quiet lanes of Arlington National Cemetery are matched gray or black. They are paired into three teams – the lead team is in front, the swing team follows, and nearest the caisson is the wheel team. Although all six animals are saddled, only those on the left have mounted riders. This is a tradition which began in the early horse-drawn artillery days when one horse of each team was mounted while the other carried provisions and feed.