When the Great War broke out between the Entente and Axis powers in August 1914, Britain faced a sobering, potentially disastrous shortage of optical glass, which had become essential for fire control, aircraft spotting and other military imperatives.

Glass becomes a strategic material

One reason for the awkward situation of Britain and other adversaries of Germany at the outset of World War I lay in dramatic changes since the mid-1800s in the technology of warfare, and the place of precision optics in it. The development of the Jena glasses itself sparked a wave of innovation across optical design. While its impact on peaceful pursuits, microscopy in particular, is well known and celebrated, the advent of superior optical glass also made an indelible mark on military ordnance.

Conflicts in the mid-19th century such as the American Civil War—for which existing weapons generally forced contact at close quarters, and even artillery could fire only across relatively short distances—generally relied on sighting by eye, and had little need for fine optics. But advances in artillery power and precision during the subsequent half-century had ratcheted up target ranges to as high as 40,000 to 60,000 yards. To fire accurately over such vast distances, those new guns demanded a new generation of optical rangefinders, panoramic sites, field glasses and other fire-control devices, which were only as precise as the optical glass in them.

In short, warfare had evolved to the point where the side with the best optics would have a clear advantage on the battlefield. And there was no turning back the clock.

Before the war commenced, Britain was importing some 60 percent of its optical glass from the German operation at Jena, with another 30 percent coming from Parra Mantois in Paris and only 10 percent from the U.K. firm Chance Brothers. Once the war had cut off German imports, Britain not only had to make up that peacetime shortfall, but also had to feed an insatiable new demand for optical munitions, as mobilization proceeded to bloat the army from a peacetime level of 250,000 soldiers to a war footing of several million.

In theory Britain had several options. It could, for example, boost its imports from France, where glass manufacture had proceeded to a quality level much closer to that of Jena than Chance Brothers had been able to achieve. But Parra Mantois was already overwhelmed with the demands of France’s own mobilization, and had little to spare for Britain’s effort. Meanwhile, Chance Brothers insisted during the war’s early months that the firm’s existing facilities would suffice to meet all military needs for what was expected to be a very short war, and resisted government prods to expand production capacity.

By late spring 1915, however, it became clear that the war would drag on indefinitely, that Chance’s optimism had been unfounded and that Britain faced a serious shortfall in optical glass and optical munitions.

Unconventional measures

Confronted by that shortfall, the British government had to scramble early in the war. Some of its initial steps included issuing newspaper appeals for private donations of field glasses, gunsights, and other optical instruments, as well as commandeering all unsold optical instruments in private and commercial hands.

It also attempted to exploit what foreign sources it could. In a particularly surreal twist, in late 1915, the U.K. even opened up back-channel negotiations (through Switzerland) with Germany—with which it had been at war for more than a year—to trade British rubber for German optical instruments. The negotiations actually succeeded, with the German War Office pledging to deliver 30,000 binoculars to Britain by the end of the year, with another 15,000 to come monthly after that. (The agreement, however, never actually went into effect.)

Ultimately, to continue its war effort, Britain needed to become self-sufficient in optical glass manufacture. To do so, it embarked on what now might be called a “public-private partnership.” In June 1915, the Optical Munitions and Glass Department of the U.K. government’s recently formed Ministry of Munitions dangled a new deal in front of the recalcitrant Chance Brothers, which included money to fund plant expansion, offers of scientific expertise, and guaranteed exclusivity in military contracts for ten years, in exchange for specific increases in military optical glass production. Chance immediately responded by increasing capacity and getting to work on reproducing the high-grade optics featured in the Jena catalog—a daunting task, as such glasses had never really been a significant part of Chance’s operation.

The project proved a stunning success. While Britain never attained complete self-sufficiency in optical glass, and while securing some raw materials remained a problem throughout the war, by 1918, according to economic historian Stephen Sambrook, Chance’s catalog “included virtually everything that had been obtainable from Schott in 1913,” as well as some things that hadn’t been. “A first-class and high-volume optical industry had been created,” he concludes, “where before the war there was really only small-scale manufacture of a very limited range.”

The fortunes of that newly built business, and that of other companies involved in British optical munitions, encountered a severe slump in 1919, after the sudden end of the war and of military demand. Yet Chance Brothers survived the slump and remained in business until the 1980s.