For most of the 20th Century, most of the world’s militaries put great efforts into denying the superiority of optical to iron sights. There were several reasons for this iron-sight bias: first, optical sights were originally fragile, and vulnerable to failure modes that iron sights were not, such as lens breakage, reticle dislocation, and fogging. Second, and perhaps more importantly, the military is an environment where hard effort is not only celebrated, it’s almost fetishized. An optical sight seemed to make accurate shooting so easy that marksmanship trainers worldwide thought of it as “cheating.” Third, sport target shooting, which was heavily cross-pollinated with military marksmanship training then as now, had rigid equipment rules that specified iron sights.
Over the years, the technical problems were solved. The toughest and most persistent was fogging, which was solved by putting an artificial atmosphere into the scope, in place of the precipitation-capable air atmosphere of old. The manufacturer suctioned the atmosphere out of the scope, and replaced it with pure nitrogen gas — no water vapor to lead to fogging. This was done for military optics at first, especially for aeronautical ones, around the time of the Second World War. Leupold shipped the first commercial scopes with this feature in 1949; rather than a new model it was a running change in production of the 2.5x Plainsman scope.
But long before that, scopes were being used for military marksmen. In World War I, miscellaneous scopes were mounted to rifles for what the Army called “sharpshooters.” These may have included the notoriously zero-non-holding Warner & Swasey Prismatic and 5x Winchester A-5.
A 1916 article in the news magazine The Literary Digest (published 1890-1938), available online at oldmagazinearticles.com, directly compared British and German optics, and noted that:
[T]elescopic and mirror sights are delicate and easily damaged, and are in consequence not well suited for general military use. There seems, however, no valid reason why picked shots detailed for special duty should not be provided with the most effective sights which exist, even if the rifle so fitted require special care.
Several optical sights have been devised, and some of them have done excellent service in match shooting. These may be divided into three classes — the use of lenses without any tube, as in the early aerial telescopes; the employment of lenses to give a reference-line, with or without optical aid, the so-called collimating sights; and finally, telescopes, prismatic or otherwise, complete in themselves with arrangements for elevation and deflection, and with means for ready attachment to the rifle.
The best known telescopic sight is that of Dr. Common, which he perfected in 1901; as regards principle it has not been improved on. The Zeiss prism telescope-sight [Presumably the Zeiss Zielklein -- Ed.] is really a small periscope; it has the disadvantage that considerable light is lost in the prisms, far more than in a simple telescope. In this sight, and in the similar Goerz prism-sight, means are provided for illuminating the cross-wires at night.
According to a frontline veteran quoted by the magazine, this illuminated reticle provided the German sniper with a considerable tactical advantage over his British opposite number.
A 1919 article in the same magazine had, along with some descriptions of sniper tactics still in daily use and some clearly optimized for the stationary Western Front, this note about equipment:
Snipers’ rifles were always the pick of those furnished an entire division, and were fitted with extremely complicated and accurate calibrated sights. Small telescopes, with scaled measures spaced upon them, gave the sniper the distance of an object while he sighted his weapon, and permitted him to tell within a few feet how far away his intended prey was stationed.
That sounds more like they’re talking about rangefinders, perhaps stadiametric rangefinders, than scopes. Follow that link if you can; there’s a great deal of interesting information about Great War sniper tactics in there.
Period American Army doctrine, which one expects to be backward and hidebound, turns out not to be silent on sniping and telescopic sights. Now, it’s not exactly voluble on the subject, either. In 1917-18 there was no sniper manual, just a single paragraph in the Small Arms Firing Manual, 1913 (corrected through March 15, 1918 with Changes 1 through 20).
253. TELESCOPIC SIGHTS.–To properly equip a special class of shots who, in action, may be employed as sharpshooters, the telescopic sight is adopted. These sights are supplied by the Ordnance Department at the rate of two to each company. They will be assigned to the enlisted men found best qualified to use them, and may, in the discretion of the company commander, be carried by them at inspection under arms.
Not less than four men of each company will be given a suitable amount of practice with these sights.
It’s interesting that this brief doctrinal mention fails to suggest any need for special training and maintenance, and fails to note the assignment and zero of the rifle to one individual. It’s simply a shooting-prize, handed to the guys who shoot best at qualification (which, then, was known-distance bullseye shooting. Perhaps we’ll have a few more excerpts from this manual in the days ahead). There’s also no mention of the painstakingly learned two-man sniper-spotter teams, search techniques, or concealment and decoy-position tactics that are the meat of the 1919 article linked above. It’s sniping as shooting, period; something that would strike today’s school-trained sniper whether from Marine, Army, SF, or SEAL sniper school as reductive to the point of absurdity.
We’re probably going to pull another excerpt or two out of the 1913 Manual, and then put the .pdf up on here for your edification.