I sent out a military squad about two weeks back to a human hamlet that should be three days away. They haven't returned yet, and they were my only squad. I've checked legends mode, and nothing seems to have happened to any of the squad dwarfs.
Is it possible to get my dwarfs back?
What did you send them to do?
If you sent them to look for an artifact, then they might be gone for 3-5 years. Especially if it's an artifact being held by someone as they can't be recovered yet.
If you sent them to conquer a hamlet, they won't come back (they're in charge at the hamlet now). You can get them (some of them?) back by setting a messenger and setting a mission to call them back on civ map screen.
If you sent them to raid and they never came back and they're not dead/captured (gone from the military screen) and you're playing version 44.12, post a save on the bug tracker.
Has the held artifact behavior worsened? I know it used to result in the squad returning immediately after leaving.
However, if you send them out to recover an artifact that's no longer in that location (but not held) the dorfs may go bar hopping around the world in search for rumors of its actual whereabouts, and there's still no option to restrict how long they'll search before giving up, as far as I know (but I'm out of actual touch with later version).
Those who have waited it out and reported that their bar hopping dorfs finally came back, seem to average 3-5 years. Not sure what the current behavior of sending out a squad to get a held artifact is.
--Edit
Sent out my military commander to fetch The Unnameable Ulcer (an elk bird bone toy hammer). Last held by some dwarf. He didn't reappear right away, so I guess that doesn't happen any more. It's the 28th of Sandstone 217. Will report back if he ever turns up again.
2nd granite 218, he's back.
With a fine report on the many taverns in the world. Including some at the southpole and one right in the middle of an evil biome at some place called Cityterror.
He didn't find anything, as expected. But seems to be working OK apart from that.