Invisible units

[the_blade]

I think I might have pressed a button accidentally but all my units seemed to have become invisible!
My cities and improvements still show.

 

[Noble Zarkon]

Ctl + I perhaps??

https://www.civfanatics.com/civ4/strategy/references/keyboard-shortcuts/

 

[lymond]

It might also be Ctl + B which toggles bare map. It's one of the buttons in the lower right to the left of the Globe button.

 

[6K Man]

If you are playing Better BUG AI (or another mod like it), you may have accidentally toggled the view units off on this menu bar