What do people thing about doing a DoW if you believe you are about to be attacked? For example, by the West just before France is invaded, by the Soviets before the Vistula is crossed. Negates the Surprise rule. The downside is reduction in the enemy factory cost and loss of your own reduction, plus 1 VP. But if it means the survival of Paris or Leningrad?
It is very circumstancial and can depend on meta game.
If you have a group in which the Axis always attacks Paris very early a premptive DoW by the West against Axis goes a long way to keep the Axis away from England and blockade positions and makes resources a real problem for the Axis production.
If you see a big opening battle of a war coming and consider all researched techs and think the DoW makes a difference why not. Typical example Sovjets see the attack on Leningrad coming.
So yes premptive DoW can be a helpfull tool depending on the circumstances.
don't forget you need to move a ground unit into a territory which if you send in suicide squad you will lose some bp, or more effective - make sure you have a decent force and send it in to pin GE one more area away from paris and fight there first...difficult to do but in later year (39ish) maybe...
Reasons: 1) If you screen your front line with cadres (pro tip), surprise is irrelevant
2) It's a 2 VP gift to one player and a 1 VP gift to the other.
3) You have made it easier for your enemy to grow their industry and lost the opportunity to more easily grow your own.
There are exactly 2 cases were I would consider it: 1) To get first fleet fire against an invasion fleet poised to attack Britain/US 2) Your enemy has a hole in their defense where you can capture either their capitol or a sub-capitol which causes the collapse of a power (e.g., Rome).
Paris is usually not worth defending unless France has survived into the mid/late game. The West has higher priorities (Britain, US survival, Blockade fighting, India, etc).
If you and me would play a game of T&T you as the Axis and me as the West, the first thing I would do before production would be the proposal of a peace treaty for lets say 3 years and offer Western diplomatic non intervention in the Balkans during this time. If we couldnt agree on peace I would build 7 British units and then dow you in Spring 36. Assuming a competent 3rd player do you like your chances of victory ?