LCD is right, and I'd suggest you use his solution.
See, if a tank gets hit on the gunbarrel or one of the tires etc. then it obviously cease to fire/move, and thus it is "dead" but the CREW may still be alive (or at least one crew member), sitting inside smoking weed or whatever...
To use the !(alive ---) would be best if you then used a pre-condition, like:
damage tank1 >0.8: tank1 setDammage 1
then the crap WILL explode once it is seriously hit, and THEN ya can use the !alive crap