For light duty use around a base in your home country a ruggedised Apple Watch might be OK, but I would have serious concerns about it for more active usage in field training or active duty, and No Way would I consider it for active deployment in a potential combat environment.
- Apple Watch even with a reinforced protective case is still a device with a glass screen prone to getting broken.
- Full function requires Bluetooth connection to your iPhone unless you have the cellular version - but the cellular doesn’t support roaming off your home network. Do you really want to carry your iPhone in active conditions?
- All versions are active Radio Transmitters which could be undesirable in deployed operation
- There have been recent security concerns about published data and trackability of similar devices around military bases. I think the original reports related to Fitbit or Garmin, but Apple Watch would be no different in this respect. https://www.wired.com/story/strava-heat-map-military-bases-fitness-trackers-priv acy/
- Battery life is likely to be a problem in deployed field operations. Fine if your duty allows you to connect and charge every day, but 2 days in the field could leave you with a disfunctional watch.
- Apple Watch has a rather bright display which lights up with arm movement, can be annoying even when simply driving at night. This can be controlled by settings, but forgetting to go dark is a potentially fatal mistake in the military world.
In summary, Apple Watch is great for off duty time and office work, but there are probably more appropriate devices for active military purposes which you suggest by mentioning Mud.