On a military base anywhere in the world, you'll find a variety of watches on the wrists of personnel. What you probably won't find is a watch that the government supplied to service people en masse, as was common in decades past. The compelling history of "issued" military watches is echoed in modern watches and marketing, but those worn by soldiers today have a very different story.
At one time, the military treated watches as any other necessary equipment and contracted out their production. Adhering to very exact specifications, many of the watches produced for military use in the 20th century have a special place in the imagination of collectors — after all, they had to be very well built, durable, accurate and practical. Soldiers were issued their kit, which included a wristwatch often made by a historic company but sometimes without even branding on the dial.
That situation makes the idea of a "military watch" easy to understand, but times have changed. While there are endless examples of watches with rugged specs and serious looks available today, soldiers mostly have to purchase their own. So if you want a modern watch with the same kind of official military links as the issued watches of old, what are the options?
Military regulations related to watches appear mostly concerned with how they fit into dress standards: they are tolerated, so long as they conform. For the US Marines, for example, "inconspicuous watches are authorized for wear in uniform," while the US Navy Uniform Regulations flatly state, "While in uniform, wristwatches shall be conservative and in good taste. Eccentric or faddish watches are not authorized."
While people often speak of "the military," of course, there are many militaries in the world and many services, units, etc. in each, with their own rules and regulations. There are many different situations, and certainly some in which a watch might be required for some activities or prohibited for others.
When a brand claims that its watches are "used by" some elite tactical unit or another, this may very well be the case. Those soldiers can probably wear whatever watch they want, and they may have chosen one that's particularly well suited to their work. Vague marketing, however, can lead consumers to imagine the kind of relationship that watch companies had decades ago with militaries. Those days are largely gone, but the "issued" watch remains a potent image in consumers' minds.
One way watch brands can show military affiliation is with official markings like the famous British "broad arrow" symbol, which was historically used to mark government property. Some examples of modern watches with the British broad arrow are the James Bond watch from Omega, homages of the Dirty Dozen field watches (the originals of which had the symbol) by the likes of Timor and Smiths, as well as even a Timex collab.
It's illegal in the UK to sell goods with the broad arrow without specific authorization, but a brand can apply for permission to use government symbols through the UK Ministry of Defence Merchandising Programme — and it doesn't seem too tightly restricted, as a number of modern watches available to the public feature it on their dials. However, these days, this doesn't necessarily mean said watch is utilized in a military context.
Going a step further, British brand Bremont has obtained permission to use the "signs, symbols and Heraldic Badges of all three services" of Her Majesty’s Armed Forces (army, navy and air force) and released a whole collection of military-themed watches featuring them engraved on the case backs. Bremont is also an example of a company that works with the military or military-related organizations and makes exclusive, bespoke watches for individual units, squadrons, etc. Other brands that make watches for military organizations include Luminox with its Navy SEALs Foundation collection or Nixon with its Regulus.
Companies that actually make watches under government contract are indeed rare, but there are some examples: CWC supplies the British Ministry of Defense, and specifically, "the CWC SBS watch is currently issued to Royal Marines, Royal Navy incl Sub crew." French watchmaker Yema is said to be an official partner of the French Air Force.
Another such company is Canada-based Marathon, which is an official United States General Services Administration contractor. Many Marathon watches have available dial options that include "US Government," the Canadian maple leaf symbol, U.S. Marine Corps logo and the logo of the Israeli military's Duvdevan and YAMAM units. The brand says that these watches are built to various militaries' specifications and "issued" to personnel, but you can buy them, too. (Here's a soldier's testimony of using a Marathon TSAR on active duty.)
There are, however, plenty of other watches available with genuinely tough specs and also that mean military look. It's well-known that many soldiers (as well as police and personnel in other such professions) choose the eminently durable, reliable and affordable G-Shock watches, particularly the 6900 series. Various brands also build modern watches to military specifications of the past, including companies that made issued watches historically. These and many others offer an experience that's more than tough enough and certainly cool enough for civilian use.