The term kamikaze (Japanese for "divine wind") dates back to the two Mongol invasions of Japan in the 13th century, both instigated by Kublai Khan. The first attack in 1274 had 40,000 Mongol warriors with 900 ships against 10,000 defending Japanese, but a severe thunderstorm hit the area immediately after the Mongol army had landed, causing heavy casualties and aborting the invasion. The second wave of the attack followed in 1281, with no less than 140,000 Mongol, Chinese and Korean invaders in over 4000 ships facing a mere 40,000 Japanese, but the fleet did not even get a chance to land before a freak typhoon hit, drowning most of the army and scattering the remnants in disarray. Before World War II, these were the only attacks ever on the Japanese mainland, and the accompanying fortuitous acts of nature -- promptly dubbed kamikaze -- were taken by the Japanese as proof of the gods' protection for their country.

In pre-WW2 era of State Shinto, the divine winds became a part of the official mythology of the country, used for indoctrination of students and soldiers. Thus, when in the desperate last days of the war the Japanese Air Force created the Tokubetsu Kougekitai ("Special Attack Force") for organized suicide attacks on enemy ships, the first mission (October 25, 1944) was dubbed Shinpuu, the on-yomi (Chinese) reading of the characters kamikaze; this name was adopted for use in later attacks as well. Still, this was not a formal designation for the corps, and the Japanese public knows them best under the abbreviated name Tokkoutai. The pilots themselves are known simply as tokkou tai'in, "special force soldiers".

Despite public perception to the contrary, the Tokkoutai pilots were trained pilots who volunteered for the job, although some brainwashing and psychological pressure were undoubtedly involved. Before the creation of the formal organization there had already been spontaneous suicide attacks, where wounded pilots or pilots with heavily damaged aircraft had opted to intentionally crash into the enemy in order to take them out as well, instead of dying in vain. According to Lieutenant Onishi, who came up with the idea, the Tokkoutai was not intended as an efficient means of warfare, but it was hoped that it would prove a strong psychological weapon that would inspire the Japanese and demoralize the Allies. And while some training was still needed, no actual combat skills were necessary for suicide missions.

All types of Japanese aircraft were used for tokkoutai operations, usually modified simply by adding a large quantity of explosives to the nose, which in some later models was detachable. Even gliders were modified into suicide assault craft, named Ohka ("Cherry Blossom") by the Japanese but more aptly renamed by the Americans as Baka Bomb (baka being Japanese for "idiot"), since they were launched from lumbering bombers that were quite easy to shoot down.

Estimates of casualties vary by an order of magnitude depending on the source. According to the US Navy's research, a total of 1228 aircraft with 2198 men on board were lost by the Japanese Air Force after October 1944, although it is not clear how many of these were actual suicide attacks. In total, they succeeded in sinking 34 ships and damaging 288, killing 738 people and wounding approximately 1300 in the process. After initial devastation during the Philippine campaign, Allied ships soon learned to use heavy armor and anti-aircraft guns to better defend themselves against suicide attacks. Prior to surrender, the Japanese had prepared over 5000 aircraft for additional tokkoutai strikes.

Japanese suicide attacks were not limited to the air force, as military tactics in ground assaults often verged on or outright were suicidal. The Japanese also developed a weapon known as kaiten, a human-controlled torpedo used to destroy enemy ships, but this never really got out of the testing phase.

Should you ever end up in Tokyo, be sure to check out the Yushukan (War Memorial Museum) in the grounds of the Yasukuni Shrine, which has many exhibits related to the tokkoutai and their naval counterparts, including many letters written by suicide pilots, an Ohka glider and an unused kaiten human torpedo. Pictures of these can be found at the shrine's website, www.yasukuni.or.jp/english/, under the "Yushukan" link.

References

http://www.tcr.org/kamikaze.html
http://www.warships1.com/W-Tech/tech-042.htm