Modern boxing

The beginnings of the modern right cross demonstrated in Edmund Price's The Science of Self Defense: A Treatise on Sparring and Wrestling, 1867
Records of Classical boxing activity disappeared after the fall of the Roman Empire. However, there are detailed records of various fist-fighting sports that were maintained in different cities and provinces of Italy between the 12th and 17th centuries. The sport would later resurface in England during the early 18th century in the form of bare-knuckle boxing sometimes referred to as prizefighting. The first documented account of a bare-knuckle fight in England appeared in 1681 in the London Protestant Mercury, and the first English bare-knuckle champion was James Figg in 1719.[5] This is also the time when the word "boxing" first came to be used.
Early fighting had no written rules. There were no weight divisions or round limits, and no referee. The first boxing rules, called the London Prize Ring rules, were introduced by heavyweight champion Jack Broughton in 1743 to protect fighters in the ring where deaths sometimes occurred.[6] Under these rules, if a man went down and could not continue after a count of 30 seconds, the fight was over. Hitting a downed fighter and grasping below the waist were prohibited. Broughton also invented and encouraged the use of "mufflers", a form of padded gloves, which were used in training and exhibitions. The first 'boxing paper' was published in the late 18th century by successful Birmingham boxer 'William Futrell' who remained undefeated until his one hour and seventeen minute fight at Smitham Bottom, Croydon, on July 9, 1788 against a much younger "Gentleman" John Jackson which was attended by the Prince of Wales.
Although bare-knuckle fighting was in almost every aspect far more brutal than modern boxing, it did allow the fighters a single advantage not enjoyed by today's boxers: The London Prize Rules permitted the fighter to drop to one knee to begin a 30-second count at any time. Thus a fighter realizing he was in trouble had an opportunity to recover. Intentionally going down in modern boxing will cause the recovering fighter to lose points in the scoring system.
In 1838, the London Prize Ring rules were expanded in detail. Later revised in 1853, they stipulated the following:[7]
Fights occurred in a 24-foot-square ring surrounded by ropes.
If a fighter was knocked down, he had to rise within 30 seconds under his own power to be allowed to continue.
Biting, headbutting and hitting below the belt were declared fouls.
Through the late nineteenth century, boxing or prizefighting was primarily a sport of dubious legitimacy. Outlawed in England and much of the United States, prizefights were often held at gambling venues and broken up by police. Brawling and wrestling tactics continued, and riots at prizefights were common occurrences. Still, throughout this period, there arose some notable bare knuckle champions who developed fairly sophisticated fighting tactics.

Marquess of Queensberry rules (1867)
In 1867, the Marquess of Queensberry rules were drafted by John Chambers for amateur championships held at Lillie Bridge in London for Lightweights, Middleweights and Heavyweights. The rules were published under the patronage of the Marquess of Queensberry, whose name has always been associated with them.
There were twelve rules in all, and they specified that fights should be "a fair stand-up boxing match" in a 24-foot-square ring. Rounds were three minutes long with one minute rest intervals between rounds. Each fighter was given a ten-second count if he was knocked down and wrestling was banned.
The introduction of gloves of "fair-size" also changed the nature of the bouts. An average pair of boxing gloves resembles a bloated pair of mittens and are laced up around the wrists. Gloves protected fighters from both facial and hand injuries, their considerable size and weight making knock-out victories more difficult to achieve.[8] The gloves could also be used to block an opponent's blows. As a result of their introduction, bouts became longer and more strategic with greater importance attached to defensive maneuvers such as slipping, bobbing, countering and angling. Because less defensive emphasis was placed on the use of the forearms and more on the gloves, the classical forearms outwards, torso leaning back stance of the bare knuckle boxer was modified to more modern stance in which the torso is tilted forward and the hands are held closer to the face.
The English case of R v. Coney in 1882 found that a bare-knuckle fight was an assault occasioning actual bodily harm, despite the consent of the participants. This marked the end of widespread public bare-knuckle contests in England.
The first world heavyweight champion under the Queensberry Rules was "Gentleman Jim" Corbett, who defeated John L. Sullivan in 1892 at the Pelican Athletic Club in New Orleans.[9]
Throughout the early twentieth century, boxing struggled to achieve legitimacy, through the influence of promoters like Tex Rickard and the popularity of great champions from John L. Sullivan to Jack Dempsey. Shortly after this era, boxing commissions and other sanctioning bodies were established to regulate the sport and establish universally recognized champions.
Further information: Professional boxing

Rules
The Marquess of Queensbury rules have been the general rules governing modern boxing since their publication in 1867.
A boxing match typically consists of a predetermined number of three-minute rounds, anywhere from three for an Olympic bout to up to twelve for a professional fight. A minute is typically spent between each round with the fighters in their assigned corners receiving advice and attention from their coach and staff. The fight is controlled by a referee who works within the ring to judge and control the conduct of the fighters, rule on their ability to fight safely, count knocked-down fighters, and rule on fouls. Up to three judges are typically present at ringside to score the bout and assign points to the boxers, based on punches that connect, defense and knockdowns. Each fighter has an assigned corner of the ring, where his or her coach, as well as one or more "seconds" may administer to the fighter at the beginning of the fight and between rounds. Each boxer enters into the ring from their assigned corners at the beginning of each round and must cease fighting and return to their corner at the signaled end of each round.
A bout in which the predetermined number of rounds passes is decided by the judges. The fighter with the higher score at the end of the fight is ruled the winner. With three judges, unanimous and split decisions are possible, as are draws. A boxer may win the bout before a decision is reached through a knockout. If a fighter is knocked down during the fight, determined by whether the boxer touches the canvas floor of the ring with any part of their body other than the feet, the referee begins counting until the fighter returns to his or her feet and can continue. Should the referee count to ten, then the knocked-down boxer is ruled "knocked out" (whether he or she is unconscious or not) and the other boxer is ruled the winner by knockout (KO). A "technical knockout" (TKO) is possible as well, and is ruled by the referee, fight doctor, or a fighter's corner if a fighter is unable to safely continue to fight, based upon injuries or being judged unable to effectively defend themselves. Many jurisdictions and sanctioning agencies also have a "three-knockdown rule", in which three knockdowns result in a TKO. A TKO is considered a knockout in a fighter's record. A "standing eight" count rule may also be in effect, in which the referee counts no higher than eight to a boxer who regains his or her footing after a knockdown, allowing the referee time to assess if the boxer is able to continue.
In general, boxers are prohibited from hitting below the belt, holding, tripping, pushing, biting, spitting or wrestling. The boxer's shorts are raised so the opponent is not allowed to hit to the groin area. They also are prohibited from kicking, head-butting, or hitting with any part of the arm other than the knuckles of a closed fist (including hitting with the elbow, shoulder or forearm, as well as with open gloves, the wrist, the inside, back or side of the hand). They are prohibited as well from hitting the back, back of the neck or head (called a "rabbit-punch") or the kidneys. They are prohibited from holding the ropes for support when punching, holding an opponent while punching, or ducking below the belt of their opponent. If a "clinch," a defensive move in which a boxer wraps his or her opponents arms and holds on to create a pause, is broken by the referee, each fighter must take a full step back before punching again (alternatively, the referee may direct the fighters to "punch out" of the clinch). When a boxer is knocked-down, the other boxer must immediately cease fighting and move to the nearest neutral corner of the ring until the referee has either ruled a knockout or called for the fight to continue.
Violations of these rules may be ruled "fouls" by the referee, who may issue warnings, deduct points, or disqualify an offending boxer, causing an automatic loss, depending on the seriousness and intentionality of the foul. An intentional foul that causes injury that prevents a fight from continuing usually causes the boxer who committed it to be disqualified. A fighter who suffers an accidental low-blow may be given up to five minutes to recover, after which they may be ruled knocked out if they are unable to continue. Accidental fouls that cause injury ending a bout may lead to a "no decision" result, or else cause the fight to go to a decision if enough rounds (typically four or more, or at least three in a four-round fight) have passed.