Until the use of gloves became common, pugilists struck mostly with a vertical fist because it was considered less injurious to the fist to hit with a vertical fist than a horizontal one, especially when using hooks or swinging punches. However, they used a horizontal fist when the target warranted it, such as to the side of the neck. The vertical fist was thought to have a greater range, but, in fact, the arm's reach does not get longer just because the fist is rotated 90 degrees, unless you make some other body adjustment.
Due to the confrontations American soldiers had with Filipino natives in the Philippines during the Spanish-American War in 1898, the guard was raised from the low knuckles downward position to the higher knuckles forward position. When engaged in hand-to-hand combat, the Filipinos would slash the wrists of the extended arms of the American soldiers.
The wearing of gloves in a boxing match is a fairly modern innovation. Prior to 1866, when the Marquis of Queensbury Rules made the wearing of gloves mandatory, boxers fought bare-knuckled. Gloves, or “mufflers” as they were called, were used only in sparring. One may think that fighting bare-knuckled, would cause significant damage to the fist. A common injury among modern boxers is the “boxer’s fracture,” in which the outer two knuckles, and sometimes the outer metacarpals of the hand are broken from the impact of an unprotected punch. Many boxing greats have broken their fists in this way when engaging in street fights.
However, the risk is significantly reduced through the biomechanics of throwing a bare-fisted punch. Old style pugilism, which was built primarily on linear action and emulated the thrust of a swor,d used a vertical fist, rather than today’s horizontal fist.