can i move troops across water in the campaign?

[Alexios]

The manual describes this, but it's not entirely clear...

To move troops from one province to another by sea you must -

a) have a port in the province you wish to leave from
b) have an unbroken line of your ships (ie. at least one in every sea area) between your province and the province you wish to attack.
c) no ships belonging to the faction you are attacking in any of these sea areas.

I believe if you are currently NOT at war with the faction at the time you move your army across the sea, their ships will not block your passage; only those factions you are at war with at the time you make the move, can block you.

Of course, once you do attack the faction (i.e., make war with them), you will not be able to move an additional stack to the target province, nor will you be able to freely move additional units after the battle is over. So you will need to deal with their ships eventually. Sometimes this is an important thing to consider prior to attacking, because your troops will invariably need reinforcements once the battle is over (the AI loves to counter-attack, esp. when you're besieging one of their garrisons!)

By the way, welcome to the Org, Better_Half!

[Motep]

so thats how you move across water...

[Kavhan Isbul]

I believe if you are currently NOT at war with the faction at the time you move your army across the sea, their ships will not block your passage; only those factions you are at war with at the time you make the move, can block you.

No, this is not correct, at least not entirely. Neutral and allied factions will not block your ships as long as you move an army from one of your rpovinces to another. However, if you attempt to invade their provinces even without being in war with them, you will not be able to do so. Just try it and you will see what I mean - if you want to attack a province, being at war or no war, you will not be able to do it as long as there is at least one ship belonging to the faction, owning the target province, blocking you ship route to this province.

[Alexios]

I tested this last night, and yes, you are very right Kvhan. Thank you for correcting me. It's funny, I've never noticed this before. But I have always played as English or Byzantium, so I guess I've always had enough land mass in front of me to keep me busy.

But as far as sea battles go, I always try to build up my navy as soon as possible from the very beginning of the game, and hopefully establish superiority in the seas. Once I have done that, then I begin attacking the faction in the water until I have cleared the lanes to the province(s) I want to conquer. Playing as the Danes, however, I am sure it would be very difficult to establish such superiority, at least in the Early and Middle periods, anyway.

Another tactic I thought of that might help a small faction looking to expand overseas, is to attack a coastal province controlled by rebels. The AI does not build ships for rebels, at least none that I've ever seen, anyway. So you would have free passage to attack their province, providing you don't have any other adversaries blocking your shipping lane. This would help you get established on another continent, and thereby expand from there.