Humans fought several interstellar wars with the Kzinti Empire, starting in 2367 and continuing for centuries. Each of four "official" wars ended with the punitive confiscation of two worlds of the Kzinti Empire, and the death of approximately two-thirds of the Kzinti adult males.
In addition to these "official" wars, there were Kzinti "incidents" both major and minor, and some count six wars, apparently including two "unofficial" wars. Kzinti tend to attack before they are ready, and have no concept of limited war. "Kzinti fight gallantly, ferociously, and with no concept of mercy; and they always take on several times as much as they can handle". They steadily lost an empire they had built up over thousands of years.
Even long after the wars, in 2850, the Kzinti population was less than one-eighth what it had been before Kzinti encountered Humans. However, they were never in danger of extermination, as their non-sentient females were largely untouched by the wars; so the next generation helped replace their losses. Puppeteers, and perhaps others, claim this repeated culling of the most warlike Kzinti resulted in an evolutionary change, producing a less aggressive and/or more intelligent species. However, the change may have been partly (or perhaps even mostly) cultural, not just genetic. After the wars, Kzinti fathers began teaching their sons that Humans are not good to eat.
First War (2367-2420?): The first war was the worst for Humans. In 2367 Wunderland was conquered and occupied by the Kzinti, and in following years Sol System was invaded repeatedly, starting with an unorganized fleet known as Gutfoot’s Horde circa 2384. Sol held off the invaders using safe ramscoop ships, a giant laser cannon in the outer asteroids (used to launch the ramscoops with light-sails) which chopped at the Kzinti ships, and smaller mobile cannon which darted in and out, using their own beams as photon drives, while Kzinti telepaths continued to report that the Human worlds had no weapons at all. Slowed by unexpected Human resistance and limited by the lightspeed barrier, the war dragged on for decades instead of years. But the huge Kzinti Empire, with its heavily armed, gravity polarizer driven starships, would have eventually won the war.
Then, in 2409 the Outsiders sold hyperdrive technology to the Human colony of We Made It. When a Human-built hyperdrive ship arrived at Sol System two years later, the crew hadn’t known of the war and were amazed at their heroes’ welcome. It was the strategic advantage of the hyperdrive which turned the tide of the war and gave victory to Humans. According to an unofficial source, Human hyperdrive armadas ended the war by 2420.
Second War (2449?-2475?): The second and subsequent wars were hardly worth discussing, at least by comparison with the first. The Kzinti always tended to attack before they were ready. During the Second War, the Kzinti were barred by treaty from owning hyperdrive motors, but had a few anyway. Gravity generators were coming into use in Human Space.
Third War (2490-?): Said to have been a bigger push by the Kzinti. Wunderlanders claim it was ended by the Wunderland Treatymaker.
Fourth War (?-2505): Officially the last Man-Kzin War, the Fourth was a desperation move, with Kzinti suicide attacks. It was highly unequal in Earth’s favor and ended in 2505 with the Covenants of Shasht. This treaty made it illegal for Kzinti to use any but police weapons, either individually or on their starships; to eat human meat; or to kill a "legal entity", which is defined more narrowly than in most Human law.
Unofficial wars: The difference between an "official" and "unofficial" war is not addressed in any official account, but since there was apparently no formal treaty ending any unofficial war following the Fourth War, it appears that these wars were not officially sanctioned by the Patriarchy, who rule the Kzinti Empire. (The unofficial wars may or may not have been unofficially sanctioned). Beowulf Shaeffer mentioned a war "in Kzin" circa 2615, long after the 2505 Covenants of Shasht. No account indicates the date of the other unofficial war, but according to Puppeteers there were six wars before 2650 .
The Man-Kzin Wars is a series of military science fiction short story collections as well as the eponymous conflicts between mankind and the Kzinti that they detail. They are set in Larry Niven's Known Space universe; however, Niven himself has only written a small number of the stories.
All of the cover art for the books in the series is drawn by Stephen Hickman?.
The first story set in the Man-Kzin Wars, The Warriors (1966), was one of Niven's earliest published stories and one of the first of what would become his Known Space series. Niven did not consider himself qualified to write war stories; therefore, although a number of his later stories referenced the Man-Kzin Wars, he never actually showed them. However, there was a large fan demand for stories covering the conflict, and a number of his author friends had shown interest in writing tales set in the timeframe. Niven therefore allowed the Man-Kzin Wars to become a shared universe, starting with the 1988 release of The Man-Kzin Wars.
Initially, there were only plans for two volumes. Niven, along with John Hewitt? (one of the main writers for the Ringworld RPG) composed a "Bible" for aspiring writers, including several pages of notes composed between the two of them and photocopied pages of the RPG. The Bible included corrections for some of the inconsistencies among Niven's work. Jerry Pournelle and Poul Anderson were among the first authors approached, and both ended up writing stories.
After the release of the second volume, reader demand was enough to allow continuing releases periodically, continuing to the current day. Starting with volume three, Niven himself has composed several additional entries.
The Man-Kzin wars
In several different stories by many different authors playing in the universe there are references to a total of five Man-Kzin wars taking place.
The net effect of these wars is summed up by a retrospective comment from Beowulf Schaeffer in the short story "Grendel": "The Kzinti aren't really a threat. They'll always attack before they're ready", because the more certain is one's victory before a fight begins, the less honour is to be had from it. With decreasingly impressive logistical and technological advantages, each Man-Kzin War results in the confiscation or liberation of one or more Kzinti colony planets by the humans. In this way humanity contacts the Pierin and Kdatlyno, former slave species, and takes over worlds such as Canyon (formerly Warhead) and Fafnir (formerly Shasht). Several of the stories of the Man-Kzin Wars depict the nearest Human colony at Alpha Centauri, called Wunderland, which was occupied by the Kzinti for over 50 years.
Eventually (in Ringworld) we learn that the Kzin reverses were deliberately engineered by the Pierson's Puppeteers, who lured the Outsiders to We Made It in the first place. This allowed the mayor of We Made It to purchase a Faster-Than-Light drive on credit from the Outsiders. Once the humans had FTL warships, the Kzinti couldn't defeat the humans in space combat.
The Puppeteers had hoped that the culling of a quarter to a third of the more aggressive members of the Kzinti with every war would result in a more peaceful race, or at least one that was capable of coexisting with other species without instantly trying to kill and eat them. This shift in Kzin attitudes succeeded spectacularly, although the Kzinti themselves do not think very highly of the changes, nor of the price they paid to achieve them. In fact, a fringe faction of the Kzinti known as the Kdaptists, frustrated with the reversals their race had suffered against humanity, went so far as to adopt the human concept that God had created humanity (not Kzinti) in His image, and that He favors and protects humans over other races.
As the Puppeteers expected, a form of "natural" selection occurred, with the more mindlessly aggressive Kzinti dying in the wars with humans, and the more moderate, intelligent, and cautious Kzinti surviving, presumably to think long and hard about the consequences of starting yet another pointless war. By the time the Kzinti attained the level of sophistication and foresight needed to win against humans, they no longer had the numbers or the drive to do so.
One of the reasons humanity is such a dangerous enemy is the psychological blind spot the Kzinti have toward human females. Since the Kzinti have bred intelligence out of their own females, an inexperienced Kzin is sometimes careless enough to leave human females to their own devices, usually with fatal results to that particular Kzin. It has been further described in the novels that a combat-trained human female is a Hero's worst nightmare. The Kzinti term for any particularly competent human female soldier is "Manrret" (singular) or "Manrretti" (plural), so named out of a sense of gallows humor regarding lethal encounters with same. From the Kzinti point of view a Manrret's stamina, speed, reflexes, pain tolerance, and reasoning capability (enhanced intuition by virtue of increased interconnectedness between the left and right halves of the human female brain) are far superior to a Man's. This gives some Kzin reason for considering each of the genders of humanity to be a separate alien species. On Wunderland the leader of Kzin has developed a bond with a human female of which only they understand.
The Man-Kzin Wars (1988, Larry Niven, Poul Anderson, Dean Ing)
Man-Kzin Wars II (1989, Dean Ing, Jerry Pournelle and S.M. Stirling)
Man-Kzin Wars III (1990, Larry Niven, Poul Anderson, Jerry Pournelle and S.M. Stirling)
Man-Kzin Wars IV (1991, Donald Kingsbury, Greg Bear and S.M. Stirling)
Man-Kzin Wars V (1992, Thomas T. Thomas, Jerry Pournelle and S.M. Stirling)
Man-Kzin Wars VI (1994, Donald Kingsbury, Mark O. Martin and Gregory Benford)
Man-Kzin Wars VII (1995, Hal Colebatch, Paul Chafe, Mark O. Martin and Gregory Benford)
Man-Kzin Wars VIII: Choosing Names (1998, Larry Niven, Hal Colebatch, Jean Lamb, Paul Chafe and Warren W. James?)
The Best of All Possible Wars: The Best of the Man-Kzin Wars (1998)
Man-Kzin Wars IX (2002, Larry Niven, Poul Anderson, Hal Colebatch, Paul Chafe)
Man-Kzin Wars X: The Wunder War (2003, Hal Colebatch)
Man-Kzin Wars XI (2005, Larry Niven, Hal Colebatch and Matthew Joseph Harrington)
Man-Kzin Wars XII (2009, Paul Chafe, Hal Colebatch and Matthew Joseph Harrington)
Man-Kzin Wars XIII (2012, Hal Colebatch, Matthew Joseph Harrington, Paul Chafe, Jessica Q. Fox, Jane Lindskold, Charles E. Gannon, Alex Hernandez and David Bartell)
Man-Kzin Wars XIV (2013, Hal Colebatch, Jessica Q. Fox, Alex Hernandez, Matthew Jospeh Harrington)
Cathouse: A Novel of the Man Kzin-Wars (1990 Dean Ing)
The Children's Hour: A Novel of the Man-Kzin Wars (1991, Jerry Pournelle and S. M. Stirling)
Inconstant Star (1991, Poul Anderson)
A Darker Geometry (1996, Mark O. Martin and Gregory Benford)
The Houses of the Kzinti (2002, Dean Ing, Jerry Pournelle, S. M. Stirling)
Destiny's Forge: A Man-Kzin Wars Novel (2007, Paul Chafe)
Treasure Planet (2013, Hal Colebatch & Jessica Q. Fox)
Annals of the Man-Kzin-Wars: An Unofficial Companion Guide (Alan Michaud?, 2001)