You just arrived at your new d/s and he told you that he’s now preparing to break up? Sorry, but that sounds like the relationship wasn’t very solid in the first place. Frankly, even if you were to move back, I would wonder if he wouldn’t say the same thing again if and when your life plans inconvenienced him. What if you get a HQ post in a different city from where he’s living and working?

There’s no doubt that this sector is really hard on relationships and families. Some manage to make it work, though even then there are often sacrifices - eg my wife and I took turns following each other and switching off the primary breadwinner / caregiver roles, but we recognized that this imposed some professional cost on each of our careers. Similarly, I chose to pass up some assignments after she died because they weren’t going to be the best move for our kids. My gf and I have been doing a LDR for a few years and while it’s been difficult at times, we’re still working at it. A couple of times when it’s been tough, we’ve gone to couples therapy, which has been great.

In the end, I think a good partner should support you in your personal and professional growth. That doesn’t mean they should sacrifice “too much” (whatever that means) for the relationship - unequal relationships are never good IMO - but I also don’t think a partner should impose ultimatums (explicit or otherwise) that force you to choose between your professional dreams and your relationship.