Pretty sure he is referring to this challenge levelhttps://www.warzone.com/SinglePlayer?Level=1234663
Starting position has a huge influence on your team's chances of winning. Ideally, if you can grab the center tile (C7), or a tile that positions you to be near to one or both or your partners, makes the battle substantially easier.
Just make sure neither you nor your AI partners starts at IT7, not sure if its a design error or intentional, but that tile starts with 2 armies instead of 20 like the rest giving the player there a major disadvantage.
In summary, look at your AI companions 1st and 2nd choices are and pick the tile that you feel would let you best support them. Be prepared that if you choose the center, you have a 1/5 chance (in my experience) of getting it.