@VDK
Not crucial, but preferred. So when brigade gets “AIRDEFENCE” order , all battalions participate in manner.
Eg, you can put SHORAD/AAA , or HQ battalion , with brigade containing SA-10 , SA-11/17, SA-15 , etc…
Take care when unmovable sam battalion, SA-2, SA-3 , SA-5 … but is ok to experiment 🙂 - SA-15 protects SA-2 for example (they are in the same brigade).
But don’t mix typical brigade -> battalion link , with this “support link” mentioned in the OP.
This is special link, as I’ve mentioned above.
It is for adding supply/airdefence to a brigade as an “external battalion” - NOT in the same brigade , but linked to it as its support., useful to add eg. SA-15 battalion to some Armoured brigade for protection.
Or Nato counterpart, “Avenger” battalion to some M1A1 Brigade.
And also, adding some supply battalion to a brigade. - again, that battalion is NOT part of the same brigade … but can be part of same division, or not, doesn’t matter.