Command Squad - how to unlock heavy artillery support?

[letsfetz]

pals

i love to play the KV-2 doctrine sith the sniper ace. (stadtkampfstrategie in the german version)

recently i also tried to get used to the advantages of the command squad.

an extra weapon of the command squad is the light artillery support (75mun). according to the description of this unit this can be extended to heavy artillery support.

however I dont get it done to reach the heavy artillery support. I already reached lvl 3 veterancy (offense or defense) but the artillery didnt get an upgrade


someone may enlighten me please 

thanks for help and best regards

[Hendrik 'DarcReaver' S.]

Leftover from 1.00. Vet 3 CS used to get access to heavy arty strikes back then.