Why World War I Helped Create The Candy Bar Boom
The journey of the cocoa bean has certainly been a long one. Its cultivation likely began with the Olmecs of Mesoamerica, who passed down to the Aztec Empire. The latter used the bean as a form of currency and as the basis for a drink known as xocoatl (via Smithsonian Magazine). Refined sugar would come later so most of these cultures would not recognize chocolate in its modern iteration as a solid food or sweet treat.
While Europe eventually became smitten with the drink once sugar was added (as opposed to the Aztec use of chili powder), it was not until 1847 that the first solid chocolate was produced by British inventor Joseph Fry. Afterward, companies either began to adopt it, like Cadbury Chocolate (which had previously sold chocolate as a drink), or form it into a solid form from scratch, like the Nestle and Hershey companies (via Bulk Candy Store). The popularity of chocolate in bar form, however, didn't truly take off until World War I.
It took a World War to truly popularize chocolate bars
Conditions on the front lines of World War I were horrific to say the least, particularly on the muddy Western Front. In previous (and later) conflicts, troops would often be on the move, the Great War's trench warfare meant soldiers and armies would remain static for months as artillery, illness, and starvation became some of the daily hurdles to survival. In an effort to provide some emotional relief, chocolate rations became increasingly common in the British and, later, American supply lines (via History.com).
In the case of America and its veterans, their enjoyment transitioned into huge domestic demand for chocolate bars, especially at a time when Prohibition would soon leave many in need of pleasurable alternatives. As old and new producers began to set up locations throughout the country, many different ingredients were experimented with as the burgeoning industry took shape. It was thanks to these WWI veterans that by the time of World War II, companies like Hershey became so well-established that they hardly batted an eye when commissioned to make products for the military — such as heat-resistant candy bars (via We Are The Mighty).