Supply Raids vs Troop Columns

[llll BlackFlag]

Can someone please explain the difference between supply raids and troop columns to me? I understand that supply raids are a reinforcement mechanism where 1 point of strength gets pushed from one region to an adjacent region and if you successfully complete the supply raid that point of strength disappears. I can't find much information on troop columns though. I've read that they are transferring "legions" between regions but this is meaningless since I don't know what a legion is and can't differentiate it from a supply raid. What happens on the strategic layer if you do or do not complete them?

[TheDarkZero]

Troop colums reduce the strength in the region by one point wen completed, are both easier to do and detect than supply raids, and they are transferring legions within the region and you happened to find a weak spot in this operation.

Think about like this: supply raids are moving strength between countries while troop columns are transferring strength between cities within the same country.

[fowlJ]

'Legion' refers to a single unit of ADVENT Strength - if a Supply Raid moves a Legion from a STR 3 region to a STR 1 region, both regions become STR 2. Detecting and completing a Supply Raid mission destroys that Legion instead.