Traditionally circumcision and pain used to go hand in hand. Later anesthesia was invented and circumcision became a medical procedure instead of being just a religious / cultural practice, and the relationship has become more complicated.
If you are getting circumcised today in a hospital having no pain during the procedure and only some discomfort afterwards is a reasonable expectation due to modern anesthetics and pain killers. You also would not expect to get life threatening infections because the operation is done in a sterile environment using sterile tools, and if you do manage to catch something it will be taken care of by antibiotics.
Even though some people don't react well to local anesthetics and they may feel some pain during the procedure, by and large it is reasonable to expect the experience to be mostly pain free.
But it wasn't the case throughout most of human history and in some parts of the world it is still not so. Anesthetics have not even been invented until the mid 1800s, and they may not be used even today during traditional circumcision ceremonies, although the world wide trend is to move towards using modern techniques and perform the procedure with adequate pain management. It is likely that most circumcised men in the world who are alive today were still cut without anesthetics. Men living in developed countries may cringe at the though of having their foreskin cut off without at least numbing it first, but in many countries circumcision without anesthetics is still common practice.
Indigenous humans on nearly every landmass on the planet practiced circumcision, mostly as a rite of passage or as a religious rite. Which points to the likely origins of circumcision as one of the trials and tribulations in a transition to manhood initiation ceremonies. One of the aspects is the pain one has to endure as one's foreskin is being severed without anesthetics, and during the painful recovery process post surgery. Since circumcision permanently alters the body someone who has gone through it has "physical evidence", that it has indeed happened.
Even today many think of their circumcision as not just surgery but as something spiritual deeply rooted in religion and culture. While I do not follow any religion that requires a circumcision the significance of the experience was not lost on me. It may be difficult to explain why, but I chose to have my foreskin removed without anesthetics. So this topic has personal significance to me, yet it is not something that I share easily. I think it is a question that is always on people's mind when the topic of circumcision comes up, and I have been asked to tell about the experience several times, so I am going to attempt to describe how it feels like.
It is not possible to give an accurate description of pain, language is just not a good device to convey that information, one has to experience it in the flesh to understand it, and even then everyone reacts differently.
I think for most people it is obvious that having your foreskin cut off without numbing the area first hurts a lot. People who claim otherwise probably don't remember their own circumcision.
Since I have experienced one version first hand, I can at least describe how it feels, although there are so many techniques, some of which are more painful than others, that any description can only be an illustration.
Also for me it was voluntary, something I cared about a great deal. I can describe the physical pain, but I have no idea how others perceive the same thing. If someone is sufficiently convinced, e.g. on religious or cultural grounds, that pain is a necessary part of getting circumcision he may perceive it as something positive that deepens the spirituality of the experience. Others who are forced to endure the pain of their circumcision certainly wish they could have avoided it. It really does hurt.
In order to understand what I am about to say, one first must consider the biological role of pain.
We try to avoid pain instinctively because pain signals injury thus avoiding it has survival value. That is exactly why it is so difficult to override our natural reaction to pain, because just casually shaking it off instead of avoiding the source of the pain would have a huge negative impact on survival. If a predator is trying to eat you or some thorns are tearing an open wound in your hide you should try to remedy the situation as quickly as possible, your survival may depend on it. Therefore the instinct to get away from pain is pretty much hard wired in our brains, and it overrides nearly everything else if the pain is severe enough. Yet, we humans occasionally find ourselves in situations where the ability to tolerate pain serves some useful purpose. One may have to temporarily endure pain to protect others, or in order to be able to fight, or for most of history even during medical procedures. Even animals can temporarily ignore pain to some degree e.g. in an adrenaline rush during a fight or when protecting their offspring. But only humans can deliberately put themselves in a painful situation if there is something to gain from it on the long run. The ability to do so may very well be one measure of civilization.
I was circumcised in a way that is probably one of the least painful that can be done without anesthetics, foreskin sliced off in more or less one cut.
So how did it feel like?
You probably have cut your hand before. Have you ever nicked your finger chopping something in your kitchen? You feel the knife going in, it stings a little and then you recoil and and pull your hand away from the pain. You don't think about it, all this happens instinctively in a blink of an eye.
Fundamentally it is the same sensation when the knife takes off your foreskin, except it is making a lot larger and deeper wound which is proportionally more painful, and you can't just pull away, the pain is only going to end when the knife has severed your foreskin all the way through. It stings like hell and you bleed profusely, in case dealing with the pain wasn't bad enough.
Mercifully the cut only lasts a few seconds if it is done right, and it is over before your brain has time to panic. It is important to do the cut quickly so as to minimize the pain. To an observer it usually looks a lot worse than it actually is.
While it is quite painful it is far from unbearable pain. Just compose yourself and don't fight it, just let it happen. It is not going to cause permanent brain damage, or PTSD or scar you for life. Probably a lot of things that happen to you in your life are more painful. Have you ever had any broken bones? Had a really bad toothache? You get the point.
Unless you have been somehow forced into it, the most likely long term psychological effect will be a boost to your self esteem. If you had your dick cut without anesthetics and you have managed not to end up crying in a fetal position on the floor that tends to make you respect yourself a bit more.
More complicated techniques consisting of lots of little cuts are undoubtedly more torturous. Certainly modern surgery, e.g. sleeve resection would feel like torture without appropriate pain management.
After my original circumcision I was left with too much loose skin and I ended up getting revision surgery. Of course that was done under local anesthetics. I felt almost guilty about it, since it felt like "cheating". On the other hand the anesthesia wore off more or less all at once right after the surgery was finished, and I was suddenly in an awful lot of pain for the next 15 minutes or so. After that I have resigned to the idea that having any sort of modern surgery performed on you without anesthetics would probably be a very bad idea.
Fortunately cultures that practice circumcision without anesthetics tend to use traditional methods typically consisting of only one or a few cuts. Although some African initiation rites do employ a lot more elaborate and very painful procedures.
Clamps and forceps that crush the foreskin apparently cause a pinching sensation, but I am not qualified to comment on how painful that is, since I have no personal experience on that matter.
Other devices may cause other types of pain, e.g. thermal cautery (popular in some Middle Eastern countries) causes a burning sensation and it also requires a longer time to detach the foreskin than it takes to slice it off with a knife. It should only be used after administering proper pain relief. It is, after all, not really a traditional instrument but a piece of modern technology that belongs to the era of readily available injectable anesthetics.
Circumcision happens to cure and prevent a number of penis problems, thus it is usually considered to be a medical procedure. On the other hand many people just do it for looks, or better sex, or whatever personal reason, not really to cure a disease. Most people would not even consider anesthetics for getting a tattoo, a piercing or getting branded. I don't think getting a circumcision without anesthetics is any more extreme, we are merely not used to the idea because the procedure is assigned to the domain of medical treatment, not body modification. But sometimes the line is a bit blurry.
Some of the earliest circumcisions were most likely performed as an initiation rite. In order to show that you are a man you have to go under the knife and demonstrate that your willpower is stronger than your fear, and you can control your urge to recoil and try to flee from the pain. Being able to resist our animal instincts is an essential part of what makes us humans different from the lesser beasts. I wish people did not forget that. There would be far fewer problems in the world if people learned to control themselves instead of impulsively indulging in every knee jerk reaction. That is what being civilized means.
I think I should mention that as far as pain inflicted as part of rite of passage ceremonies goes circumcision must be somewhere in the middle. There are less painful, or merely symbolic initiation rites. There are also really horrifying ones, such as almost whole body scarification, or ingesting poison that may kill you or cause permanent brain damage, or repeatedly being stung by bullet ants where you may die from the shock of the pain or from an adverse reaction to the venom injected. Snipping the skin off your dick does hurt but not nearly as much as some of these.
People who oppose circumcision tend to overstate the amount and severity of physical pain. Moreover the effect the pain has on a person cannot be understood without context.
Most horror stories about how painful one's circumcision was usually come from someone who did not even want to be circumcised in the first place but he was coerced into it or even worse he was physically forced under the knife while kicking and screaming. Such an experience is likely to be traumatic and dehumanizing, pain or no pain.
Others who went through essentially the same operation and suffered the same physical pain but willingly, without being forced, often remember the event as something positive, a rite of passage to be proud of.
It is meaningless to compare experiences without context or to make blanket statements what should be considered barbaric. It is the perception of the person who is being circumcised that counts, not what others imagine to be right or wrong according to their own beliefs.
