With apologies to Nancy Sinatra.
Without giving away too much information, some Trail scenarios of mine are going through playtesting and one of the comments (heavily paraphrased) was 'I'm surprised by the amount of combat in the scenario.' That made me think about combat in the abstract: what use is it, can you have too much or too little, and is there an assumption that Trail scenarios have less combat than BRP?
Incidentally there are going to be some very mild spoilers here for certain BRP scenarios and campaigns (Black Devil Mountain, Masks of Nyarlathotep and Tatters of the King in particular) so if you really would rather not know, read no further.
When Call of Cthulhu first came on the scene it followed in the footsteps of Dungeons and Dragons, which was an extension of Chainmail, which was itself an elaborate form of wargaming. The whole point of the system was combat. What your character wore, their religion, their alignment or any other non-combat facet of their character paled into insignificance compared to the amount of damage your character could deal and absorb in a combat round. Ever since those halcyon days fantasy gaming has had a love-hate relationship with combat that has yet to be resolved, but the chief difference between fantasy combat and horror combat is that, in fantasy, the heroes are expected to win handily. In horror, as has been mentioned before, all victories are pyrrhic, and defeat is not uncommon. That made the early Chaosium scenarios little more than combat-heavy bloodbaths, which is probably how the game got its reputation as a character-killer. D&D had much the same problem with character death during the early levelling process, but once you survived past fourth level, gained a few hit points and had more than one spell at your disposal, your odds of survival increased significantly. BRP wasn't like that. If you went into a combat situation your odds of survival were always low, and as combat situations were the meat and drink of the scenarios available at the time you tended to die a lot.
In game, this meant that the players were plunged into situations that seemed pretty hopeless at first glance. It also meant that clue-finding took a back seat to gunplay. Black Devil Mountain is a fairly typical example of this tendency. Though there are clues to be had, none of them really matter very much to the narrative. The whole point of the scenario is to funnel the characters towards a combat moment, and more time is spent detailing the specifics of that moment than, for instance, describing the cabin that the protagonist inherited, even though the cabin forms part of the hook of the scenario. The players could ignore every NPC, march straight towards the combat zone (which is pretty clearly signposted from the start) and go in guns blazing, which that would be just as valid an approach to the challenge posed as finding clues. In fact it was probably more valid, as it solved the problem quickly, where clue finding tends to be a slow, uncertain process in BRP. Though this combat-heavy approach could result in exiting scenes, I think most current players of the game would agree than these early scenarios proved beyond doubt that you could have too much combat in a horror game.
More elaborate campaigns were just as bloody, though not as quick. Masks of Nyarlathotep, which is still considered a classic of the genre, wanted more clue-finding but in the end was a series of combat encounters, some of them bloodier than others. While there was some scope for occult inquiry and spell casting, ultimately it came down to a massive battle scene. Players and Keepers alike accepted that this was the natural way of things. There was a balance to be had between combat and non-combat play, and the exact nature of that balance was up to individual preference.
Things changed. The roleplaying market in general began to prefer story-driven games, and BRP was not immune to this trend. Fast forward a few years and now we have Tatters of the King, the polar opposite of Masks. In games designed along Tattered lines, combat takes a back seat to clue finding. The presumption is that the only solution to the problem - to any problem - is to think things through, gather information, and use the right occult tools for the job when the time comes. Going in mob-handed will not solve the problem; it will complicate it. Meanwhile on YSDC Keepers wonder how to rein in their turbulent players, having firmly convinced themselves that gunplay has no purpose in a game like Call of Cthulhu. Yet this is merely an assumption, and like all assumptions it is open to challenge.
In Trail the game has taken one step further and made finding clues part of the core mechanic of the game. BRP's percentile system placed no weight one way or the other; you could put points in combat or in non-combat skills, and both choices were equally valid. Whether the scenario was or was not combat heavy was largely a matter of preference, not game design, and as preferences changed so did the published scenarios. Yet in Trail the clue-finding mechanic often doesn't involve a contest at all, and finding clues is the purpose of most of the scenes in any given scenario. This is so central to the system that it may be easy to presume combat always takes second place, or that Purist gameplay (as opposed to Pulp) has no combat at all.
I am not convinced this is so.
First, there's the question of challenge. All roleplaying games feature challenge of some description, which the protagonists then have to overcome. Typically in a narrative the protagonists face several different challenges of varying difficulty before encountering the climax. In this progression, combat has its uses, even in Purist style play. Particularly in early challenges, combat can provide victories which in turn boost the players' morale. Morale is always important in gaming, but in horror it has a special purpose: it convinces the players that they have a chance, even when the odds are stacked against them. That hope, even if it is an illusion, draws the players back again and again. It won't matter if they lose in the end, so long as they believe, going in, that they had a chance of winning. Defeat under those circumstances is, in its way, just as satisfactory as victory, inasmuch as player agency - the belief that the actions of the player matters - is preserved. If the players start to think, from the very start, that they have no agency, then they're not going to have much fun, and nothing shatters agency quicker than a series of seemingly inevitable defeats. A quick, victorious combat against mooks, or even the occasional heavy, gives them reaffirmation of agency, and that can only help the game.
Second, there are going to be times when combat serves to demonstrate the power of the enemy more effectively than any other mechanic. There is a reason why Fleeing is an important skill in Trail. There are only so many occasions when finding a blob of ichor or a crabbed note in an occult grimoire will suit the narrative. Clues like these are the sizzle, but at some point there's got to be some steak to go with that sizzle. It may be a steak they can't handle; it's probably better for the narrative if it is. In game, these are the times when the big bads show up and lay waste to everything in sight. NPCs tend to die a lot in these scenes, and there may be a few player deaths as well. That's kind of the point. Without an effective demonstration of power the players have no reason to worry, any more than (in real life) most people worry too much about the rats in their basement. They may accept, in a vague kind of way, that rats exist, and are probably closer than they'd like to think about, but they don't break out the shotguns and dynamite to deal with their rat problem. Combat scenes provide a reasons for the players to get proactive about their steak - to mix those metaphors as thoroughly as possible!
That's my take on combat in Call, and Trail, of Cthulhu. It's not that it has to be the be-all and end-all, as it was in Black Devil Mountain. Nobody wants to go back to the days of Dungeons and Shoggoths, where 9 out of 10 investigators had a Tommy Gun and the 10th one was schlepping around a box of dynamite. There is such a thing as too much combat, and I think horror is more suited to a story-driven than a combat-driven style of play. That said, combat does have a legitimate purpose, even in a clue-heavy game like Trail. It provides challenge, reinforces player agency, and demonstrates the power of the enemy, all of which are as important to the narrative as clues are.