It's not a zero-sum game, but you're not the only player in the game. There are also other factors to consider: If everyone just sat back and grew as fast as possible, the game would be very boring.
I agree. Building up your army for 50 turns, and then moving in and crushing people with your massive high tech army is indeed a very boring strategy.
Moving a pre-existing army around does not actually cost you anything in terms of growth, unless you are attacked.
I need to stress that this game is slightly different than a regular game in that everyone started with some troops, which they would typically need to spend a non-trivial amount of time and resources producing. Being able to send raiders out on turn 1 for free does make the dynamic very different. So yeah, there is almost literally no cost to sending these troops out as raiders, and you can deal quite a bit of damage with them.
If you stop the growth of 2 players for 5 turns, you would only lose 4 turns of growth. If you target the two closest players, this weakens your biggest enemies more than it weakens you.
2 turns for 5 turns was an example of what would be a huge success in raiding. In reality you would be more likely to get 3 turns for 2 turns.
The thing is, any attack earlygame is pretty certain to cost you more then it will cost your enemy as long as they react properly. While it is possible to make huge gains (see NQT in
this game) it relies to a large extent on your enemies screwing up.
The reason for this is that it takes a very long times for troops to reach your opponent, which while not a huge deal when its turn 50 and you have armies that took 20 turns to make, is a huge deal when its turn 10 and it takes three times as long for your raiders to reach them as it did to produce them. The reason for this is that in the time your troops are walking over, they can produce better troops for the same cost (eg. you send 3 spearmen against them, but by the time your spearmen reach them they can easily defend themselves with 2 pikemen, or if you send pikemen, they can defend with halberdeers, if they send knights, they can defend with dragoons), or simply have more labor in the time it takes them to reach you (so while you can spend 6 labor (3 turns production at turn 6), they can spend 6 labor (2 turns production at turn 11), and at the end will be a turn ahead in production).
The game is not built so that you can only either grow or produce a military.
It isn't, but early game troops cost nearly the same, while being far weaker than lategame troops, and production is fundamentally the same (1 city can produce at maximum 1 troop per turn). That means that while someone that makes a army with 30 pikemen will have a much stronger army then you for a long time, you will eventually be able to counter them with dragoons, no matter how many pikemen he tries to send at you. But if I am attacked before I am ready to send max quality troops out, then I will build an lower quality army if I need to.
But here again I am defended by the fact that it takes such a long time for enemy troops to reach me that I will have more labor (with which to produce more troops) and better buildings (with which to produce more troops) by the time their army can reach me.
In addition, this is cumulative, if my enemy spends 10 turns fighting others, then I will have 10 turns more growth then him, which will allow me to build a stronger army than he can build, even though he has spend longer building his, I will have spend longer building the foundation for my army.
And if everyone else followed your advice, they would be too shy to send their armies out to face yours as it razed their outskirts.
No, not at all. You seem to think my strategy is "Do nothing but grow even if they are attacking you and razing your land". My strategy is "Grow as much as possible, and
always be prepared to defend yourself". If someone send troops near me, I will build troops sufficient to defend against them, even if they promise not to attack with them.
If someone is going to attack with an army I can't stop easily, then I will try to make alliances and everything in my power (including stopping all growth) in an attempt to stop it.