Suppose several allies all do spy attacks on an enemy op that has a large number of tanks (or vehicles) just before there own forces arrive to attack. Would the spy attacks stack to cause nuke level weakening? Or is there some complication I don't know about? Do you know anyone who has ever tried that tactic in a war?

It will half, then half again, then half again, up until you hit 1 (if the enemy forces are on the op you're attacking). Quite often done

Thanks, I suspected it would work like that, but I don't think I've ever been in an alliance that tried it before.

well ik you got it clear but i want to clear one kf the terminologies , by allies you mean your alliance members right and not players of other alliances who are friendly.

well this a term of confusion , just last week or so malice and i , were on the other side of the argument and later we came to know that we were taking allies in different means.

Yeah, I meant my alliance members. Someone should come up with a different word for one of the definitions.

it wouldn't matter either way. if a spy attack is successful then the units on that op will be affected either way.