Sword & Planet fiction (S&P) obviously has some relationship to Sword & Sorcery (S&S). They both have swords, right? In my opinion, both subgenres of fantastic fiction emerged out of a similar cultural background, during the period from WW1 through to the end of WW2. Like S&S, there have been periodic revivals of S&P every few decades, although often mixed with other genres or subgenres of fiction. This mixing of different influences goes all the way back to the beginning of the subgenre. Although I'd like to think that one of the influences is the pulp-era Westerns, which might strike some as odd.

Before I go any further, perhaps a brief summary of what goes into a Sword & Planet tale, at least of the traditional sort. You have:

1) A protagonist. This is a man from a relatively civilized time and society, who nevertheless doesn't quite fit in. Often he is just too manly and honorable for the culture he is surrounded by. This has an obvious parallel with the idea of the “barbarian outsider” in Sword & Sorcery fiction. The protagonist in many pulp Westerns is a drifter or adventurer-type.

2) The protagonist goes somewhere, usually suddenly and mysteriously. Even if he began the journey willingly, the destination turns out to be far from what he expected it to be. Also, he can't get back easily, his means of transportation being destroyed or not under his own control. In more modern genre parlance, basically a “portal fantasy.” Pulp Western protagonists of the drifter or adventurer-type obviously move around a lot, always wanting to see what is over the horizon or on the other side of the mountains or desert.

3) There are strange natives. Even if basically humanlike, the cultural expectations are somewhat alien compared to the place the protagonist came from. However, he might actually fit in better here than in his original society. The clash of cultures is a common element in Westerns whether it be dealing with railroad magnates or Indians.

4) Speaking of natives, the protagonist encounters a lovely female who has a big problem. Whether it be an unwanted marriage arrangement, a hostile city about to declare war, or simply being lost / stranded in the wilderness, this problem is serious enough that she could use some help. The protagonist, being usually an honorable sort (or at least wanting to impress the lady), volunteers to give assistance. There is almost always a woman involved in a pulp Western story, even if only as a background element. Whether a good woman or a bad one, she offers obvious motivations and complications to the protagonist's life.

5) After a series of perils, chases, duels, rescues, and other adventurous deeds, the protagonist and the lady find they have fallen in love. Even if they could not stand each other at first meeting, their shared dangers result in mutual admiration developing. This is pretty much a given in most pulp-era adventure tales, including Westerns.

6) They make plans for a future together, normally becoming engaged or married. However, new perils await the happy couple... at least if there are to be any sequels. Finding a good woman and settling down is often the long-range goal of every decent man in a pulp Western.

It might be helpful to think of the S&P subgenre in terms of “generations” of authors and characters.

1st generation: Edgar Rice Burroughs and immediate imitators such as Otis Adelbert Kline and Ralph Milne Farley. 1910s to early 1930s. The big one here is of course John Carter of Mars.

2nd generation: the pulp magazine era, specifically Flash Gordon and Planet Stories. Often quite a bit more raygun action than swords (in modern terms a healthy dose of “planetary romance,” but you need to remember that our modern concept of “genre divisions” was created by publishers later for marketing purposes). Perhaps you've heard of Eric John Stark? Lasts until about mid-1950s.

3rd generation: the S&P revival of the 1960s and early 1970s, following the similar S&S revival. Moorcock's “Old Mars” books, Lin Carter, Mike Resnick, John Norman's early Gor books.

4th generation: an echo of the 3rd generation revival from about 1979 to the mid-1980s. This was kicked off by the space opera revival following Star Wars in 1977. Flash Gordon cartoon in 1979, movie in 1980, Blackstar cartoon in 1981. Even “science-fantasies” like Krull and some strains of post-apocalyptic fiction like Thundarr the Barbarian got into the mix.

So finally, my main point: Sword & Planet, much like Sword & Sorcery, really came from a mashup of different influences (just consider the various strains Robert E. Howard mixed together to create Conan's world). From tales of wandering knights, to supernatural / alien horrors, and even pulp Western gunslingers and WW2 GIs, these are tales of manly men facing danger and making the world a better place (or at least slowing its decline - even if unintentionally by destroying evil men and monstrous creatures).

Spencer E. Hart dabbles in writing adventure fiction in various genres. His Sword & Sorcery tale “The Brides of Bmapth” appears in Warlords, Warlocks & Witches. Currently working on something that might count as Sword & Planet, or at least Planetary Romance with other genres mixed in. Occasional progress reported at his blog.