In this guide we will take the whole Scandinavia area starting with Sweden.

Our aim will be efficiency as Sweden as only 4 military factories in 1936. We will also have to act quickly before the world tension gets too high.
We will learn how to best use special forces like Marines and Mountaineers, and which technology to choose.
At the end of this guide you should get the Northern light achievement.
Playing this walkthrough with Sweden is a pleasure as we will use interesting war tactics to create and lead an interesting political faction.

(side note: I am playing in French, so some of the terms I am using could be mistranslated or confusing. Let me know in the comments if something needs a correction)

First things first, to attack your neighbors you need to be a fascist/communist faction.
In order to so, first thing to do is to hire a fascist politic counselor. It will take a while before you get fascist, but that's fine as we will prepare ourselves until then.

So, we have a political advisor advising us to go fascist. Fascist party is getting bigger day by day.
Until it reaches 50% we have some time.
As you can see we have only 4 military factories, 3 research slots and 2 naval factories. Here’s what to do with it while waiting for the Fascist party to take the power.

Civilian production
We will aim for long term and put our first focus on building a max of civilian factories (normally 4-5 military factories will be enough).

Research
Don't go into Air, Tanks or Naval. We simply do not have the factories, nor the research slots for that. Just forget them.
First, to go for the long term, always put the priority on civilian technologies.
Then look for small weapons technologies as this will be the base of our army. Then for special forces & supports units.
If you still have some slots available, go for military doctrine.

In short
1-Civilians
2-Small weapons
3-Special forces & Supports
4-Doctrine
Avoid Tanks, Air, Sea

Naval forces
Just group all your forces in one fleet that should be put as patrolling in the Baltic sea.
You can set your factories to produce only the level two ship you have.
Do not worry too much about these: you are stronger than Norway, Denmark & Finland.

National focus
First priority - Go for the politic tree on the left. You can't unlock the lower part as long as you are not fascist, so you will have to wait. But don’t forget it as it can give you extra manpower but also it is mandatory to let you create your own faction.
Second priority - Then go for civilian factories.
Third priority - Military factories
Forth priority - Land army

Counselors
As soon as you are fascist or at war, change your economic policy to military economy and increase your conscription (you will lack manpower).
Then go for bonuses to civilian production (aim for long term), then military production, then bonuses to soldiers.
No need for tanks, air, naval, motorization. We can't have these anyway. And our naval forces are much stronger then Denmark/Norway/Finland.
If you have spare points of politic power, just keep them to have enough points for war justification.

Military
Just produce Mountaineers and Marines when you can (as explained lower start with up to 8 mountaineers then up to 8 Marines).
Factories should only do small weapons, support and artillery. Spread your few factories as needed.

Preparation
As soon as you turn fascist start the justification of war against Denmark.
As soon as you have enough diplomatic power go for the justification of war against Norway.
Next priority with the diplomatic power is to go for more manpower.

Attack
Sweden has nearly twice the amount of troops than Denmark. But if you attack through the sea directly you will lose your manpower slowly and loose the war.
The trick here is to send your troops via a naval invasion while keeping your main force waiting to cross by foot.
Organize the see invasion will take up to 45 days to your troops. So that means that you should do your tactical plan before the end of the war justification.
Divide your 10 normal soldier’s units in 2 piles and keep the cavalry as a separate one.
- 5 troops should wait in front of Denmark (at the river crossing).
- 5 troops should be set to a naval invasion starting from the port south of the river crossing towards just next to Copenhagen
- Cavalry should be set to a naval invasion starting from the port north of the river toward north of Denmark.

As the war starts you will then be able to get Copenhagen via two fronts (one inland, one crossing a bridge).
The cavalry will attract some resistance and normally be beaten, but this is fine. The objective is to request attention from Denmark.

As soon as you have manpower left (as you are fascist you can turn the reserve pool to 2.5%/5% normally), start the production of 5 to 8 mountaineers.
They will be helpful against Norway.

We will create two fronts

- South front on the shore to take their capital. There put your 10 units of soldiers and cavalry. Be as aggressive as you can.
- North front with your mountaineers. Be as defensive as you can.

On the south the objective is to take the capital as fast as you can.
To go even faster, you can set 5 troops for a naval invasion starting from the port west to Stockholm to end left of Oslo.
As soon as Oslo is taken, go toward the north and point their new capital. Be aggressive.

On the north the objective is to keep their army busy with your mountaineers. Just keep your ground.
Attacking people in the mountains is difficult especially if you are in lower number. So don't take the risk.
Wait for the main army to come.

If by the time of attacking Norway, you already have navy forces, use them for the south front and put some more normal soldiers to the north.

As soon as the production of up to 8 mountaineers is over, start the same with marines.

(Don’t forget to start the war justification while fighting Norway)
We will again make two fronts

- South front with a naval invasion from your marines (5 to 10)
- North front with your main army and mountaineers (8 to 10)

South front will be a naval invasion. Be aggressive as you won't face a lot of defense.
Get first on the western shore then attack the capital as soon as you can.

North front: you will face a lot of defense. Be defensive and aim for the new capital after the fall of the first one.

You can now create your faction (if you have chosen the right national focus in the politic tree).
That's it you have now the Northern Light achievement!

Looking forward you can
- Attack the Balkans if England is not protecting them (prepare the war justification already while you're attacking Finland).
- Look to add Eastern countries to your faction (Hungary).
- Improve your relationship with the Reich or USSR.

Good luck and may the force of the northern light be with you!

Britain warns me against the Reich.
Just tell them "ok we don't go with the Reich anymore" (-100 to relationship).
Otherwise they'll declare war on you.

Britain guarantee Finland
You can just restart then. This happens as world tension is too high.
That means either that you were unlucky as other countries (Japan, Reich) declared too much wars, or you were too slow.
Remember, justify the war goals as soon as you can against Denmark/Norway/Finland.

How to use the army experience?
Focus of course on the improvement of Marines, Soldiers and Mountaineers.
If my understanding of brigades is correct,
- first try to get the right amount of troops (10 brigades) per unit type (Marines, Mountaineers, Normal)
- get the supports units (engineers, communication, recon, healing).
Try to avoid artillery as you won't be able to produce them effectively.