Handgun shooting stance

When did law enforcement/military transition from teaching proper pistol technique from one-hand-the-gun, the-other-hand-on-the-hip to the present two-hands-on-the-gun?

Female police recruits receive handgun training
in the early 1900s.

Was there any particular reason for this? Steadier holding of the firearm seems most likely, especially at longer range, with the new stance. Perhaps harder for an opposing person to snatch a gun from someone holding with both hands.

But quicker acquisition of target, quicker move to shooting stance, and less propensity to tunnel vision seem benefits of the old school practice. You also have a hand free to help repel and attacker, or to use in a blocking motion while bringing a handgun to bear on an attacker, with the old school method. You can keep that free hand prepositioned near a spare mag or speed loader. And shooting single handed allows you to present a lower profile for an adversary to target.

Having my earliest instruction under the guidance of WWII and Korean vets, I initially learned the single hand approach. I've mostly shot two handed the past decade or more, but at times just feel more comfortable going old school.

Having proficiency as a one handed shooter also has advantages if one hand is impaired by a hand or arm injury. Isn't that why military fliers were often issued revolvers instead of semi-autos as survival guns? Semi-autos typically require a second hand to work a slide.

Also wondering if hotter pistol loads played part in the push toward two handed shooting.

Why the questions? I'm watching an old Civil Defene newsreel on TCM... and they're showing volunteer "auxilary police" being trained one handed.

Pretty damn funny, actually, that Turner Classic Movies is probably the only U.S. TV or cable channel airing CD training films.