It seems slashing is much more powerful than thrusting, and thus, much more useful. Is there any technique to enhance power of a thrusting attack to the level of a powerful blow?
If not, what is the point of pointed weapon? E.g using a long stick vs light armored target, a thrusting attack will hardly do any damage.
Thrusting AND Slashing are both useful
It might "seem" slashing is more powerful because it involves bigger movements, and depending on the weapon, you feel, in your arm, that you're getting more force... but... it's not.
Thrusting concentrates more force onto a smaller point, allowing better penetration. Stabbing weapons tend to cause more lethal wounds (getting deeper to organs or major arteries). Thrusting tends to give less telegraphing and usually has better range.
On the other hand, stabbing attacks tend to have less short-terms stopping power - people often don't realize they've been stabbed, and can continue fighting back. For longer weapons, if your weapon is stuck in the opponent and they're fighting back, you can be in a bad situation.
Slashing tends to do more shallow wounds, BUT it's better at muscle damage which reduces your opponent's ability to fight back, and the force can move/maneuver the opponent's limbs or body into a position that allows you to follow up better.
This is the reason, around the world, throughout history, you can find a combination of thrusting and slashing weapons everywhere. There's usually only some periods where it goes particularly one way or another based on armor needs or conditions in which folks are fighting. (Heavy armor leads to a lot of thrusting weapons, folks having to convert farm implements, grain cutters or machetes get a lot of slashing implements).
Improving Thrusting Power
In this case, "power" means harm in such a way to debilitate quicker.
There's the classic piston-stabbing action, used with short knives and makeshift shivs - you keep stabbing the same area to try to turn it into hamburger. This is a common method in prison fighting.
"Twist the blade" is a term people use a lot, but depending on the blade's strength, the handle you have, and where/what you've stabbed, it may not really be feasible. "Jerk it around" seems to make more sense in actual situations - stick it in, jerk it around, to forcibly move the opponent and widen the wound channel. Again, this is going to be shorter blades, though the spear example would be to stick them then walk around or shove to pin them.
There are several locations which do much greater damage by targeting. Eyes and neck are pretty obvious examples for all weapons. Other organs also make a lot of sense, though the ribcage protects a lot of them requiring either good angling or heavier weapons to get past the bone.
With a thrust, I have all of the weight and power of the weapon behind the striking point. It's going to archive MUCH more power, and pressure.
Also it takes up less space than a slash. To slash, you have to create a large amount if movement, not to mention getting the angle perfectly correct (which takes years of practice)
The question is not well phrased. It's like asking "Which is a better tool: hammer or screwdriver?" (Answer: it depends...)
The better question is "which is a more effective martial arts technique?"
There is no historical basis to support the claim that slashing weapons were generally cavalry weapons.
Here are some relevant historical examples:
Swords were by far the preferred weapon for cavalry in the 1800's. Much preferred over revolvers even.
The British issued their cavalry a curved saber primarily designed for slashing. This is because of the lessons they had learned in India and Afghanistan where slashing weapons heavily predominate.
The French, however, issued straight cavalry sabers and were heavily trained to use the point. The superior deadliness of the point to the edge was known in Europe since Roman times. Traditional dueling wisdom held that one wound from a sword point equalled three injuries from the edge.
In French vs. British cavalry combat, it was discovered that very few French would emphasize thrusts instead of slashes (usually only French officers would rely on thrusting in combat). The French learned that in the heat of combat, slashing is the natural reaction of even very highly trained cavalrymen.
In Roman times, the gladius was relied upon for six centuries. It was primarily used for hacking down an enemy (often after knocking him over by slamming into him with the shield) The gladius was generally used for stabbing mainly for the coup d'gras.
Metallurgy had progressed far enough by the Sixteenth Century to allow swordsmiths to make sturdy , thin, light, fast thrusting swords. For dueling, a long, thin, sharp sword (although expensive) was a vastly superior weapon to any slashing weapon of the time (like a cutlass) Additionally, pikes (long spears for stabbing) were very successful battle weapons (even against poleaxes - i.e. hacking arms-although there was no clear dominance. Mainly it was less expensive to equip a body of troops with pikes, and easier to train them.
Then, of course, there is the obvious example of the Japanese katana. For two thousand years, the Japanese never saw a real need for thrusting weapons.
Modern military blade fighting strongly emphasizes thrusting techniques, probably because slashing techniques do not work as well against people wearing modern clothing and carrying kit belted and strapped to their body.
Nevertheless, Asian bladed martial arts place the emphasis on slashing -primarily out of centuries old traditions that rely on disarming an opponent FIRST (by slashing his hands and arms) then going for the kill.
Perhaps the most timely and relevant historical example is the example of the World War One trench raids. That was probably the last great era of hand to hand combat in close quarters, almost always at night, and almost always begun as a surprise attack. It was a time when an individuals' personal choice of weapon and technique was very likely to make the difference between life and death. Trench maces make good museum pieces, and they were used alot, but their prevalence in war museums doesn't mean they prevailed in the trench raids. British and French trench raiders tended to rely on thrusting weapons such as poignards, bayonets (often attached to a broomstick to make a pike), the "French Nail" (a bent tent peg) and Bowie knives. The British Gurkas however, gained fame using kukri (hacking) swords.
I want to emphasize I am not an expert, but it is worth looking at history. Most of the real slashing weapons (scimitars, sabers) were designed to be used from horseback. Slashing was less likely to get the weapon stuck, which was an even bigger problem when on horseback then when fighting on foot.
(The famous curve of the Katana which was largely used in a slashing was apparantly mostly about being able to draw quickly. It is also worth noting that Katanas were used more often in duels than in warfare where samurai more often used Yari, a thrusting spear.)
Also, a thrust puts more of the force behind a single point, greatly increasing the pressure (pressure is force divided by area, and is particularly important if trying to pierce armor).
To help understand the difference between a thrust and a slash, consider some hopefully familiar movements:
a cricket bat... if you "slash" with the bat you can hit a cricket ball 100 metres or more in the air, while if you prod at the ball with the end of the bat it might only go a few metres. On the other hand, if you had an everyday door to get through and swung the bat at it, it might create a dent but not open the door, while a firm shove with the end of the bat would open it more or less as easily as pushing directly with your hands (depending on distancing and how much speed you build up before/during contact).
a front kick on a heavy punching bag - a stabbing/trusting action - can easily get the bag to swing past 45 degrees, while a turning/roundhouse kick might struggle to get 15 degrees. The same front kick might struggle to break a loosely supported baseball bat handle though, while the turning kick was just fine.
Ultimately, they're both strong in different ways:
The slashing actions have more speed at impact but far less mass directly behind the strike, so their power transfers well to light, unsupported objects, but a heavy or braced object will absorb it all quickly and have relatively little overall momentum imparted (with a larger proportion of the energy quickly dissipated in other ways such as sound / air pressure and localised deformation and stresses on the struck material).
The thrust impart far more overall energy but more slowly, which can result in a more efficient transfer of momentum.
(There are a very few actions which achieve a "best of both worlds" power, with more coupling of the "slashing" action to the core body rotation, perhaps most obviously the "ridge hand" aka "reverse knife hand" strike).
Depending on what you hit, there might be time for the greater power of a thrust to accumulate and cause more localised damage than the speed of the slash allows, or the target might yield steadily over the time of impact and reduce the peak impact and meaningful damage.
The size of the striking surface is also relevant to peak power, and whether there's localised damage or more large-body momentum transfer, but it's not quite so simple as saying thrusting always involves smaller surface area than slashing motions... pick-like weapons even the score in that regard.
Ultimately, whether one or the other is more effective depends a lot on the striker's strength and speed compared to the target's rigidity and the amount of inertia it's got to overcome to get out of the way.
Is there any technique to enhance power of a thrusting attack to the level of a powerful blow?
As usual, good body mechanics are the key. I wrote this answer before about what it takes to deliver a good reverse punch, and the same principles apply here: start with bent knees, develop a connected power chain through the knees, hips, shoulder, elbow, hands, weapon - all strongly snapping and focused in the direction of the target. Using a weapon well doesn't mean moving the mental focus out to the weapon and moving it first - ground everything in your body and have it initiate the movements. Practice the same movement you'll do with the weapon while not holding the weapon, considering the mechanics, power and speed - even striking targets/bags with your hands to help give you focus and feedback.
Pro tip: a slash is considerably less useful than a proper cut. Also, a thrust doesn't require nearly as much power as a slash/cut because you're using a much smaller contact area, hence the pressure is much higher (it is science). Which is why the side of a needle doesn't hurt nearly as much as the point end, even if you push really hard.
