For the purpose of Countermeasures. Several points in the Rulebook note that they are performed "before the game begins" such as Initiative, a Classified card draw or Deployment, but the Countermeasures Classified draw specifies "when the game begins." When is this?
I would perform the draw immediately before the first player's turn. I.e. after all deployment has been completed, but before the first player's tactical phase, at which point the cards need to already be present.
That is the way we played it last week. It certainly has to be before you have a chance to cycle the cards, and I think it's by design that you have to choose your datatracker before seeing what comes up.
I don't have a rules citation right now, but based on the chunk of translation I did the other week, most rules treat the tactical phase of the first player's turn as the 'beginning of the game'.
