Black cross?

[RPKUPK]

What is the black cross insignia on certain naval units that never seems to go away?

[LiquidSky]

The black plus means the unit is set to recieve *NO* replacements/reinforcements.

It can appear on any unit set this way. A white plus means it is a priority for replacements/reinforcements.

[RPKUPK]

OK.
How does it get that way?? I'm aware of the green cross on the unit page, to re-enforce or not. How does the black cross appear and how does one get rid of it?
Of course I want to reinforce my weakened units (naval), and I aim to place them in a high value port hex. They get a green cross on the unit. I've never ever seen a white cross.

[AlvaroSousa]

Select a unit, upper left hand corner if the unit information panel 2nd button down.
Priority select is on the 2nd row panel divider to the right a green plus

[RPKUPK]

OK, that worked, thanks. I had no idea, now I know why certain units weren't reinforcing. I had never activated that, nor selected it.

[AlvaroSousa]

I believe every button has a hover tooltip.