Why do brides stand on the left during a wedding and grooms stand on the right?

Long ago, the right arm was considered the sword arm of most fighting men. If a man had to protect his bride, he would hold her with his left hand, and fight off attackers with his right arm. The reason that men may have had to fight off others was because quite often women were kidnapped. Family members naturally wanted to rescue the stolen brides. Sometimes even during the wedding ceremony, the grooms had to fight off other men who were desirous of their brides, along with the bride's family members. So having his right arm free was an important strategy. This tradition is followed today by when facing the officiant, having the bride stand to the left, and the groom stand to the right.