[shinyknight]

In history,we have seen great civilisations reach great heights only to crumble in the very end.Most of these have been studied in great details and I present some of these factors.

1.Military.
Conquerors.Might is the key.Crashing the oppostion brutally."Follow me and live or defy and taste my steel."
Double-edged.Some leaders are so successful that the whole continent is under theirs.However the large expansion of terriorties creates a new fear:Lose of it.In trying to support it,resouces have been overstretched and in short a country can't have the land of the world.

2.Trade and adventure
Merchants.Profits is the key.Making contacts,expand the range,be willing to dare.Frustrating opponents by having the goldpot while they have remote ports.Over-charged them."If you want it,pay me"However,by doing so,they have made enemies.Either they will form an alliance against that country or they too promote navigation.Discover new trade routes and the monopoly is destroyed.

3.Peace-Lovers
Neutral Party.The key is when facing the aggressor,they rather give in and provide support than fight.They are spared of the cruel fate of being held prisoners.Remain friendly relationships with the aggressor."If you can't have a friend.don't make an enemy"The people are happy.Independent have been achieved in an unusual way.But not every case is like this.Some are being dragged to fight,choosing a side.Some are still being invaded after offering treasure.Some are being cut-up like a pie.Though,the country has not been lost,it is forced to accept humilating terms.Worse,neutral party may be hated by both sides over their indecisive nature.

More coming?I don't know