I fully agree with the need to launch a bold offensive against the English right from the beginning as otherwise they will just send one army after another into Wales. They are richer than the Welsh, so they can better afford the attritional battles in the Welsh hills. They are also the only other faction with strong archers.

The Norwegians, Scottish and Irish don't have any archers that can compete with your Saethwyr archers. Saethwyr have the additional advantage of being able to plant wooden stakes, making a frontal cavalry charge against you suicidal, although stakes don't stop enemy infantry.

Your main advantage is that the English forces are thinly spread and they start off relying on weak militia units to defend their border settlements. This advantage will disappear in time, so you need to act quickly.

Your king, who also happens to be your national hero, starts off in Montgomery, along with a reasonably large army. My preferred strategy is to move the entire garrison, including the catapults, across the border to capture Shrewsbury in the first turn. Your king is the hero of the Welsh people, giving him a command bonus when fighting the English, so you should
make use of him.

Before you launch the attack, make sure that you replace the garrison in Montgomery with the units from the fort to the west of the city, and that your king has recruited all the available mercenary units. You will need the extra men to occupy the neighbouring forts.

During the first few turns, your settlements should be concentrating on producing additional troops, despite the strain it will put on your finances. Caernarvon will be your most important recruiting centre in the early stages as it starts off with the facilities to train a good variety of
units, including Saethwyr archers.

As your army crosses the border, you will see an empty English fort guarding the border crossing. Move one of your weaker units into it. There are many permanant forts scattered across the British Isles, all of which guard potential invasion routes. When you take a settlement, you should always try to take the nearby forts. Even a fort guarded by a weak unit will
delay an invading army, giving you time to move your field armies to where they are needed. Each permanant fort gives a free upkeep for two units, so you lose nothing by occupying them.

Shrewsbury is only guarded by a wooden wall, so your catapults will have little difficulty breaking through, and your army should easily overwhelm the garrison. After the battle, make sure that you occupy the nearby forts before the English do.

After another few turns, you should have recruited enough troops in Wales to be able to mount simultaneous attacks on Chester and Cardiff. Remember to send reinforcements from Montgomery to Shrewsbury so that your king can turn south and attack Gloucester at the same time. Money will be tight at
this point, and you may even be running at a loss, but don't panic. Capturing the settlements will increase your income, while the casualties you endure will reduce your costs.

As you may already know, religion has been replaced with national culture in this campaign. There are no priests, and the purpose of churches is to convert the inhabitants of a region to the culture of their rulers. Most units in the campaign can only be recruited if their culture has sufficient hold over a region. This means that you will be able to recruit English units in the newly conquered territories, but if you hold on to your gains, English culture will fade away and you will only be able to recruit Welsh units instead. Many
of these English units will be a useful addition to your armies, and recruited units will remain with you even after their culture disappears.

You will now find that the English are starting to deploy the forces they have been busily recruiting in their remaining provinces, which will force you onto the defensive until the barons rebel against the crown.

When the Barons Alliance emerges as a faction, they will take some of the pressure off you, and they will probably be receptive to an alliance proposal. Your goal should be to arrange for the war between the king and the barons to be a stalemate, leaving you free to pick off the occasional province. If the barons win, their leader will become the next king of England, and he will be looking for somewhere to expand to.

If the barons are defeated, they will sometime attempt to rebel again by generating a mission in which you are asked to capture an English settlement and hand it over to the barons in return for money and an alliance. They will keep on trying to rebel against the king until both English factions have been wiped out. Remember that if the English are on the ropes, you don't need the barons, and if the English are doing well, the barons are unlikely to get very far without a lot of help.

Keep an eye on the conflict in Ireland, and try to ally with the Irish. If the English conquer all of Ireland, they will be free to land armies on the Welsh coast. If the Irish are victorious, they will less of a threat as they have weak archers and limited heavy infantry. You will eventually need to get control of Dublin, but there is no sense in launching such an expedition until the English threat has been greatly reduced.

The Norwegians are a potential threat, but they are generally more interested in Scotland so try to maintain friendly relations with them, but keep a respectable number of soldiers garrisoned in Wales just in case.