Disconnecting Old Wall Tube

I'm trying to replace the p-trap under our bathroom sink and the wall tube is stuck in the wall connector. I'm afraid they may have soldered or welded it, I've tried to hammer it to see if it was stuck from rust but it just seems to damage the tube. Any guidance would be appreciated, the house was built in 1965 and I'm not sure if anything was replaced as far as plumbing before we moved in.

Thanks for the pics. Always helpful.

If you grad the chrome tube and crush it near the fitting you night break the 50 yr bond it has made to the brass fitting. cut the tube and leave an inch or 2 will make it easier to crush. . Depends on how much of the tube is inside the fitting. Probably only an inch or 2

Thanks for your advice, I did that for a while and made a bit of progress. I ended up crushing the tube and trying to get parts that I could grab along the sides. I was able to unscrew and remove the brass ring between the wall tube and the "stub out", however, it looks like the pipe goes a lot further in than I thought. Even with the ring removed, this thing isn't budging. I'm not sure if my next step will be to remove the nut sealing the stub out and the wall tube, that thing really, really doesn't want to go anywhere. The parts on planning on using to replace the p trap are PVC and I don't have anything to cut the stub out pipe. Any thoughts would go along way. Thanks guys.

Attaching more pictures: very sorry about the disgusting stuff in the drain, but wanted to show how the pipe looked and how far in it goes.

Or, just remove and replace the old brass adaptor.

I tried to grab the wall tube and pull, ended up crushing it and only having some left to pull on now. I was able to unscrew and remove the brass ring between the wall tube and stub out, but it hasn't loosened the tube at all. I appears that the wall tube extends into the stub out much further than I thought, I tried to attach some pictures but they may have been too big.

Is the brass adapter the big nut? Because that thing is not budging. I'm going to try some WD-40 to see if that helps at all.

Check the nipple coming out of wall with a magnet. If it's steel Don't try to remover the brass adapter or the nipple going into the wall.

use a wood chisel or a solid flat tip screw driver and try splitting the tube.
Just be careful not to damage the brass fitting.

This is peeled back from front edge of fitting so just split tube and you should be able to peel it out.
Don't give up ! You're almost there.