First Fire question.

[Jumbo]

My opponent moves an unconcealed squad into an Open Ground hex adjacent to my concealed half-squad in a building hex.
No First Fire.
My opponent then attempts to move into the Building hex containing my concealed half-squad, which "bumps" the concealment counter off of my half-squad, and forces the moving squad back into the prior (Open Ground) hex.
May I then First Fire at the squad with my now-unconcealed half-squad?
Thanks?

 

[zgrose]

My opponent moves an unconcealed squad into an Open Ground hex adjacent to my concealed half-squad in a building hex.
No First Fire.
My opponent then attempts to move into the Building hex containing my concealed half-squad, which "bumps" the concealment counter off of my half-squad, and forces the moving squad back into the prior (Open Ground) hex.
May I then First Fire at the squad with my now-unconcealed half-squad?
Thanks?

Yes

A12.15 "... and is subject to possible Defensive First Fire...." about 9 lines down.

 

[buser333]

My opponent moves an unconcealed squad into an Open Ground hex adjacent to my concealed half-squad in a building hex.
No First Fire.
My opponent then attempts to move into the Building hex containing my concealed half-squad, which "bumps" the concealment counter off of my half-squad, and forces the moving squad back into the prior (Open Ground) hex.
May I then First Fire at the squad with my now-unconcealed half-squad?
Thanks?

Yes. Even twice if you like as they spent 2MF trying to enter the building.