There are three different strategies that I like to play when I play as the Vikings. I will not say which is the best because that is for you to determine yourself when playing. First though, I want to go over the big strategic mistakes many first-time players make.
Don’t overextend your first invading Leader.
The English look weak at the beginning of the game and it is tempting to use all your movements to take as many English cities as possible but the English get to roll first and they will get the support of Fyrd Units. You want to keep your only leader on the board strong enough so that the English cannot counter attack him and remove him from the game in the first Round. You also want to keep your leader threatening enough that the English must worry about where he could attack. There is no rush to take cities to win the game since the game is at least 5 Rounds long.
If you follow this first advice, all three strategies that I will cover could work for you.
Strategy One - Northumbrian Bastion
This strategy is all about taking ground and holding it. Northumbria has the fewest English defenders and is the easiest to hold against counter attack. It is also relatively easy to take all four cities in your first turn and to hold it. Once you control the North, there are several choke points that are easy to defend. If you keep a strong leader up there throughout the game, the English will not be able to take it back.
As new Leaders invade, you can push into Mercia where there are lots of cities to take, giving you the necessary number of cities to win the game. The English will get a lot of reinforcements from Wessex though and they will counter attack in force mid to late game. They will only attack from one front though since you should maintain control of everything to the north. When the English use conversion or rebellion against you in Northumbria, your northern leader can quash them.
You also want to leave single Norsemen along the paths where the English must move to attack your northern cities. These single units will waste an entire English army’s turn and really slow down any English counter offensive.
The Northumbrian Bastion strategy is especially fun to play with the War for Land and Gods Expansion. Build Forts along your front to give you extra Berserker attack dice. As your front moves south, you can convert these forts into Viking villages that give you extra Norsemen reinforcements.
Strategy Two - Wessex Control
The goal of this strategy is to minimize the number of reinforcements the English receive. Wessex gives the most English reinforcements, so that is where you attack first. Wessex is generally heavily defended, especially if the English get some reinforcements before you can take the city, so you will lose men and cannot overextend yourself. You need to leave enough men behind that it is not easy for the English to take back a Reinforcement City, so I generally don’t take more than three cities in the first turn.
After Wessex is secure, you should focus on taking any other city on the map that give 2 or more English Reinforcements with your leaders that invade on future turns. Throughout this game, you should ignore all the cities that do not give reinforcements until the very end of the game. By that point, the English should not have enough Units on the board to oppose you.
When playing with the War for Land and Gods expansion, I like to try to win by removing all the churches with this strategy. I take out the churches on reinforcement areas first and ignore churches not on reinforcement areas. By the end of the game, the English are more worried about defending their remaining churches rather than taking back reinforcement cities. Since the English get fewer reinforcements, the benefit they get from the Christian Wrath’s extra Fyrd units is minimized.
Strategy Three - Mercian Raiding
With this strategy, you are always striking the English where they are weakest and trying to maximize their loses. To do this I take a few Mercian cities the first Turn but keep my leader’s army strong. Mercia is in the center of the map, so it gives that Leader a lot of reach. The English cannot effectively defend all the cities you can reach and will either spread out or concentrate their forces for a counter attack.
In future turns when I have more leaders, I attack the cities where they have the fewest Units and let them waste men and moves taking cities I have already taken. I use my leaders first attack to attack a vulnerable city, and then I take another vulnerable city closer to the center of the map. This should keep the English scrambling to defend their vast kingdoms.
When the English counter attack, they will lose valuable troops since the defender gets to roll first and they do not get Fyrd. You should not worry about losing cities since anywhere they lose men taking, you can always take back with one of your leaders. Just keep the English scrambling to defend everywhere.