When you say to declassify everything and "fight in the light" you are either trolling or speaking foolishly. You wouldn't leave your ATM card and pin on the street regardless of which philosophy you follow. Yes, you can say the thief made a choice and it is his actions that caused you to lose all your money, but the outcome was predictable and you initiated it.
You wouldn't divulge your plan to fight the enemy you would protect it. You would protect your unit locations, orders and encrypt your communications to prevent the enemy from gaining an unfair advantage. Likewise you would try to discover the enemies locations and plans to give yourself an advantage. All philosophy aside, war is pragmatic and fairness plays no part. All of this calls for keeping secrets and a system of classification.
Negative. Your analogy does not hold. My ATM card is my ATM card. My government is my government. My ATM card does not belong to others. My government does belong to me. Further, my government professes to defend liberty above all else; my bank professes to defend my money.
Further, my government professes to be a representative government. By hiding information from me, a citizen, it is keeping me from being informed and making informed choices; thus, it cannot truly represent my interests.
As for the talk of tactics and strategy in war, this is not something about which I have not spent hours thinking. My ideals certainly commit me to thinking that any expeditionary wars are dubious, at best. However, fighting to protect one's life and liberty at and within the borders of one's country poses no theoretical difficulty. If the nation being attacked is truly representative (i.e., truly respects the liberty and autonomy of those within, and without, its borders), then there will be few, if any, enemies of said nation within the borders. Thus, knowledge of where the fighting is occurring and what tactics are being used is not necessarily destructive to the cause.
However, history demonstrates, time and again, that when liberties are given over from the people to the state in exigent situations in order to provide security, these liberties are never given back to the people from the state. This bears out as far back as Herodotus and Thucydides. When these liberties have been recaptured, they have been just that: recaptured. And, quite frequently, in more violent struggles than the original struggles which resulted in the surrender of said liberties.