Military watches were born out of an essential need - survival.
Exactly when wristwatches first started being worn in combat situations is very unclear. Some say that the German Imperial Navy wore timepieces made by Girard-Perregaux as early as 1880. Others believe that British soldiers during the Boer war (1889-1902) or that the Japanese personnel involved in the Sino-Japanese war (1894-1895) were the first to don wristwatches.
Either way, the men's wristwatch did not come to public attention until 1904, when famous Parisian watchmaker Louis Cartier designed a wristwatch for his friend and aviation pioneer Alberto Santos-Dumont. The Santos model did not become available to the public for another seven years after this, just three years prior to the outbreak of the First World War.
Even though the idea of a wristwatch had started to gain acceptance by 1914, many of the watches worn by military personnel at this time were modified pocket watches. As such, they had big cases with prominent "onion" crowns and were often attached to a strap via thin lugs that had been welded to the case. The advantage of these timepieces was their large, legible faces, which remains one of the calling cards of military watches. These modified pocket watches became known as "Trench Watches".
During World War I, American company Hamilton produced wristwatches specifically for the US Army. Before the war was over, companies such as Omega and Elgin had also been drafted to supply the forces with evermore essential timepieces. After the war, it became more commonplace and socially acceptable for men to wear these wristwatches, thanks to the many soldiers returning home from the conflict. By the time the Second World War loomed, it was the norm.
America devised the MIL-SPEC during the 1930s, which was a stringent set of criteria that all kit intended for military use had to meet before being approved. In those days, only watches that performed up to the MIL-SPEC standard were deemed military watches Stateside.
Meanwhile, at the same time in Britain the need for high-quality military watches had reached a critical level. Many British watchmakers had shut up shop and moved overseas or ceased operations entirely as the threat of World War II marched across the continent. As a way to solve this, the British Army commissioned a new wave of timepieces to be constructed by 12 companies, each selected on their individual merits and standing in the world of horology. These companies and the models they subsequently produced became known as "The Dirty Dozen." The twelve companies comprising the Dirty Dozen are Longines, Vertex, IWC, Grana, Jaeger-LeCoultre, Lemania, Buren, Eterna, Timor, Omega, Cyma, and Record. Today, these pieces are regarded as some of the most collectible timepieces ever made.
Following the Second World War, the idea of what made a military watch military solidified, and while there have been many interpretations and attempts at updates or homages, the archetype laid down by the early Hamilton Khaki models and the Dirty Dozen watches pervades. New technologies such as tritium lume and multi-function quartz modules are common in modern military watches but do not find as much favor among collectors, who prefer the designs that were born of necessity and carried the free world to victory.
Popular brands producing military watches in 2019 include Hamilton, Vertex, IWC, and Marathon.