Ok, tricky question....

it occurs optionnal deployement at the beginning of a mission, if propose by the mission (example : 2 * Threat level and optionnal deployement) and/or if rebels "play" an ally!

BUT can we have an optionnal deployement even if not propose by mission and without any rebel's ally? (I know, in this case, no threat to pay, but with some agenda cards, we've some special discount )

Thanks

If the mission doesn't specify an optional deployment, then you can't do it.

You can't have any threat unless the mission specifies you to get it beforehand. The first round, the Imperial player has zero threat (LTPG Pg. 10) and threat is only received as part of the Campaign Status Phase (LTPG Pg. 11), which the at the end of each round.

If your agenda card says, "play during an optional deployment of any mission", then that's when you play it.

You are correct; if the Mission Setup doesn't have a Special Setup that gives you an optional deployment, you couldn't play your agenda card.

If the players choose not to deploy an ally for the mission setup, you don't get an optional deployment and you couldn't play your agenda card.

You would have to wait until the Status Phase, where you would get an optional deployment.

Thank you for all this points, it's a confirmation needed, but logical...