https://www.quora.com/How-menacing-did-cavalry-charges-feelA few years ago, I was in Boston during the world series on a business trip. None of the people I was with had tickets to the game, but a few of us decided to walk down to the stadium to check out the action anyway. When we arrived, the police had barricades up so we couldn't get too close, however a local warehouse was playing the game on a TV so my group and about 100 other people were watching. After a little while, the police directed us to a main street. When we got there, I couldn't believe my eyes. In addition to half the population of Boston, there were lines of riot police and 15 or 20 horses lining up on the far end of the street. Once the police got organized, the riot police marched toward us in columns and spread out, then the horses came up the middle. Turns out horses with armed men on them in riot armor look HUGE when they are coming at you. When that wall of horses and guns advanced into the crowd, believe me when I say, we MOVED. They pushed probably 1000 people out of their way with no problem whatsoever. The horses weren't even charging in at a sprint, they were merely steadily walking toward us. Even at that slow speed, they had the same effect as driving a huge bulldozer into the crowd. Seeing this up close and personal is when I realized cavalry charges must have been fucking terrifying to have coming down on you.
So to answer your question, very very very menacing.
I have no idea of the shear terror they must have felt over 1000s of years, I once had a brief insight into what it must have been like but with out the death and mayhem.
In the mid 80s I was on a narrow cobbled road one night with 1000,s of other people when we were charged by mounted police in body armour, swinging batons into the crowd, there was no where to run to because of the weight of 1000s of people behind us pushing forward who did not know what was happening and the high walls of the 19th Century factories either side of the road, it was terrifying, literally bowel wrenching, vomit inducing stuff of nightmares.
The noise, the lights, the helicopters, the steam coming off the crowd in the night air, the missiles likes rocks, ball bearings, bottles etc raining down at the oncoming police, and then, the thundering noise of horses hoves on cobbles, it was incredible. I remember being monetarily mesmerised by the sparks coming off the cobbles caused by the horse shoes on the mettled road, before choosing to get low and not be trapped against the walls of the street, and then to follow the horses, dont ever get trapped between the mounted police and the riot police in full body armour who are following the cavalries shock and ore as not only will the horses get you on the way back the so will the those on foot and a beating like that can be life threatening.
No one died but plenty of heads were bloodied by the batons and limbs hurt by people falling, being crushed and hit.