Kendo is a Japanese martial art based on traditional swordsmanship. Practitioners face each other using flexible bamboo swords while wearing protective gear and try to strike specific locations on their opponents' bodies. Kendo is derived from traditional Japanese swordsmanship. Swordsmanship was usually practiced with wooden swords (bokuto), but this is because they are cheap and durable, not because they are safe. A solid blow with a bokuto can easily injure, maim, or even kill. Because of this, the main form of training was the repeated practice of prearranged patterns of attack and defense (kata). But even in kata practice, the participants must be careful not to strike each other in earnest, usually stopping short of the true target. In order to simulate the chaos of a real fight, less realistic but safer equipment was employed. The first development was the fukurojinai, a piece of bamboo with its end split into a number of pieces and covered in leather, hardened by a coating of lacquer. While not as dangerous as a bokuto, the fukurojinai is still a stout weapon, capable of inflicting serious injury. Hence an even safer version was developed, the modern shinai, which consists of four staves of bamboo joined together at the tip and handle. The shinai will flex when struck against a solid object, absorbing much of the power of a blow. However a blow from a shinai is still quite painful and can often leave a welt. So in conjunction with the shinai, protective gear (bogu) was also developed. The bogu of modern kendo protects the head, hands and wrists, chest and abdomen, and the thighs and groin. Prior to the Second World War, kendo was still strongly influenced by individual schools of traditional swordsmanship. Since the war, kendo has become homogenized, and the techniques optimized for competition with shinai, rather than battle with real swords.
When students start studying kendo, the first types of practice encountered are footwork drills and suburi (repeatedly striking an imaginary opponent). After basic footwork and striking comes uchikomigeiko, in which the student strikes an actual target, either someone else's shinai or a person in bogu. Then comes kirikaeshi, which is essentially a standardized form of continuous uchikomigeiko. After uchikomigeiko comes kakarigeiko, which while appearing similar is actually quite different. In uchikomigeiko, the student is either told or shown where to strike. In kakarigeiko, the student must choose where to strike, and attack continuously. Usually 15 to 30 seconds is enough to wind the practictioner. All of these kinds of practice can be done by a student without bogu. Once the student has become comfortable with these types of practice, he is ready to begin wearing bogu, allowing them to participate in other types of practice, such as wazageiko (practice of specific techniques of both attack and defense), more advanced kakarigeiko, in which their partner actively tries to thwart their attacks, and finally jigeiko (free sparring) and competitive matches. Along with the above types, kendo retains the practice of kata with bokuto. As there is some inherent danger using wooden swords in partnered practice, brand new students do not practice kata until they are at least comfortable with uchikomigeiko.