Read in a book that the Japanese carried katanas and charged into their enemies, but when everyone has guns was it just suicide? Also how often did this happen? Have fights between two or more sword wielders ever happened?
This is a fantastic question. I have a few good sources for you to check out, in hopes of answering this question: 1. 'On the topic of Hand-to-Hand Combat' by Captain S. Feldman, and, 2. A resource put together by myself 'logging' all known melee events: http://www.cqb-team.com/cqbforum/viewtopic.php?f=4&t=2192.
All in all. Sometimes it was effective. Sentry takedowns were rare but did happen, on occasion, successfully. It still however remains to be rare. Fights between two or more swords? I personally have never heard of this.