I view "at the girth" as meaning the stirrup bar and toe at the girth, with the stirrup leather hanging perpendicular to the ground. And behind the girth is that the stirrup is brought back such that the stirrup leather is no longer hanging perpendicular to the ground.
The first is correct, it has nothing to do with the US cavalry and a lot to do with the area right behind the girth being the most sensitive, and easiest place to get your leg around the horse.
Having the leg too far back means raised heels and ineffective aids. Posted via Mobile Device
I ride English and I was taught the same as what smrobs posted above. My legs do go back for certain cues but the "ideal" I think is being properly aligned.
I ride hunt seat so I keep my leg underneath me with heals down. Ear, shoulder, hip, heal all in alignment. Much better balance this way. But as said by others, it depends on your disclipline and the saddle you use.
For me, at the girth is my 'neutral' position. Behind the girth is to manage the hind quarters and just in front of the girth is to manage the shoulders. I bump/squeeze in the neutral spot to increase speed but that's about it. Although it also depends on how a horse has been trained. If I shift my outside leg back and close my inside leg on neutral my horse will lope, if I leave my inside leg off the girth my horse will move sideways.
There is no right answer. It is all technique. If I had a highly trained horse, and was an athletic, skilled rider, I might well ride with my heels under my hip to make it easier to give lots of leg & heel & spur cues. The Cavalry had to deal with quickly training thousands of riders, many of whom had no natural ability, to ride OK trained horses across rough ground. Cueing was less important than keeping learning riders to stay on horses who might stop without warning or change directions without being asked. Sounds like me...
The old style western seat, with feet far forward, worked well for average riders riding green horses in rough terrain far from any help. It also worked based off the style of saddle used.
Riding doesn't come with absolutes. If I were you, I'd ask my instructors WHY something is good or bad. Jumping uses a different position than dressage which is different from cutting which is different from polo, and all of them are different from what I do riding my marginally trained mare with my low goals & expectations. Any good instructor can tell you, not just WHAT to do, but WHY it is a good thing to do. It is only by understanding the WHY that you can understand what you are doing.
Agreed on asking "Why." The object of leg position has more to do with keeping your body quiet bc that is what keeps you on the horse. The more quiet your body, the deeper and heavier your seat and that keeps you sticking to the saddle/horse.
Disagree re: putting your feet in front. A chair seat makes you more vulnerable to falling behind the motion of the horse. You cannot maintain a chair seat for hours and hours. If you ride with a chair seat I recommend very long trail rides to retrain your legs.
Agreed re: US Cavalry. They trained, during WARTIME, many green riders, often on green horses, hence the S-shaped, long shanked, high ported curb bit with a chain. The manual gives advice on how to spend your long days drilling, then grooming the horse and cleaning and maintaining your tack.
During PEACETIME, they also drilled, groomed and cleaned/maintained, plus they had a lot of horse shows. We spent a few years hanging with the US Cavalry Assocation in Ft. Riley, KS. They have a lot of photos and data regarding the post WWI Cavalry. They would show English, jump horses and mules, single, Roman-Style, and maybe 3x/time, and their horses pulled caissons over hilly terrain. They were, at that time, trying to create a super-horse that could do it. In 1942 they discovered it wasn't possible. The peacetime Cavalry were really horse show people.