Struggling with Crusader Kings II. Help wanted!

[Culthrasa]

Been beating myself over my head how to get this achievement (one of the few i have left to do). So for the 0,2% of the people who actually got it, spill your beans!

What I tried
Been doing 10+ games on 1.3.3 with the following varying results:
- going full army, conquering Africa then trying to cross the Med, didn't work.
- Not picking Anti Colonial focus but holding off and allying with Russia till after axis defeated, didn't work
- under 1.3.3 it seems my factory output is severely less and don't have enough Inf kits to arm enough troops.
- Also under 1.3.3 Portugal builds 7inf 2art support Art, AT, Eng which are just too much to break (or go around).
- watch Youtube . One good video i could find and he made it look easy

What worked best
- Rolling back to 1.3.2
- going marine+subs to invade Portugal, worked but tension so high that doing the same to Belgium just leads to war with the Allies (even before Axis declare war).
- after Portugal, build up, then declare on Spain(goes axis), conquer it, then France and the lowlands, get Germany to capitulate (Russia helps to quicken that by draining Germany's stockpile). Problem: by that time it's 1942 and USA entered the war meaning I have about 1000 divisions arrayed against me, an untakeable Channel and Allies in Italy meaning they have a solid way to kick my behind (just not enough manpower to hold that, and all the ports and Africa and have some left to deter Russia who has "strategic reasons to be hostile".
- Even Para's won't do much good at that point when the allies have 20k+ air units.

Questions
1. Stick with Anti Colonial focus, Marines and subs?
2. What composition for Marines? 4 mar. 4 mar + sup art. 6 mar. 6 mar + sup art or something else?
3. How many Divisions? seems like I need 10 to simultaneously invade three ports (under 1.3.3 there is no way i can head on conquer them with Portugal's Infantry setup and amount. Even then I have to catch them with their pants down which seems impossible (the keep 1 to 4 units in their ports always under 1.3.3. Under 1.3.2 it is doable).
4. How to conquer Belgium (preferably in 1938).

A "you sir are doing it completely wrong, this is how you do it" is also appreciated if it comes with the perfect and failproof strategy.

 

[Culthrasa]

Went and did another try on 1.3.3, managed to get portugal and a PC, but the shoreline for belgium is just too small to properly invade... sigh...

 

[Grimmedslug]

I recently came back to play a game of HOI4 on 1.3.3. to complete this achievement, and it wasn't too difficult, considering how haphazard my plans went (I was playing while chatting to a friend while also being drunk so I wasn't really controlling my armies). I got it in my first game.

Turned off historic foci, not that it made much difference, just that turning off gives a chance that UK picks the South African Development focus before I left the Commonwealth, and free factories are a good thing. It also means that most of the time Poland starts their own faction rather than join Allies, which isn't too important, but is nice. It means one less country competing with you in warscore for the states you want, because dead countries don't make demands on the peace conference table.

My priorities on focus tree were political -> naval (for free dockyards) -> industrial. Teched and built destroyers and marines (5 marines with Support Art, 6 divisions). I found destroyers preferable because Portugal will build nothing but Destroyers as ships, and I don't want Subs to fight that. Independence, took Liberia, then conquered Portugal. Although here my distracted state got me punished because Portugal killed my marine divisions, but at that point I was building proper divisions which finished off Portugal, even if that took awhile more because I had to move them all to the islands for a naval invasion of Portugal.

At this point I switched my navy over to building 4 carriers (I was only able to realistically build 2 before I declared the war against the UK) while waiting for Germany and Soviet Union to get into their catfight, and once they did I waited a bit for the front to stabilize before declaring war on Nationalist Spain. My goal here was to gain warscore against Germany, and in 1.3.3. the Soviets apparently win Germany every time. Japan somehow didn't join the war against the Soviets, so the war ended when Germany and Italy fell. Using my warscore, I managed to take a state in North Germany (the one with Kiel Canal) which I used as a staging base into the UK so as to avoid the English Channel, which the AI is apparently hardcoded to defend. I based my fleet there, which now has 2 carriers and a bunch of destroyers. In the meantime UK is still committing their fleet to Japan (actually eventually succeeded in taking out Japan after I declared war on them, before Soviet Union then proceeded to take a war on Republic of Japan, but that really didn't change anything because I had a British Isle foothold by that point).

Declared war on UK, called in the colony puppets I got from Portugal to expand the South African front, then use some divisions to crush Denmark (also an Allied member) and naval invade into Scotland. Proceed to march into London while my army in South Africa takes out the other colonies. At that point it just became a waiting game to get the events to fire.

I didn't tech properly, and my land doctrines were terrible, I actually took Mobile Warfare with effectively no advantages until I got to the Desperate Defence line which gave me more manpower. I managed to get approximately 60 divisions of 8 Art/7 Inf/1 HTD with Support Art, Support RArt, Eng, Rec, Hosp by the time I declared war on the UK, and took the isles with 20 divisions while keeping about 30 divisions in South Africa and 10 divisions for combined home defence/Denmark. Probably wasn't very efficient because of attrition and large combat width but at that point it really didn't matter.

 

[Diados]

When I did it, it was basically the first thing you tried. Cleared Africa (war with both axis and allies), then across the med, up to northern France, and across the channel.

The key thing to do early is to flip US communist to keep them out of the war. Other than that, cross the med and the channel with paratroopers instead of Marines (to take the initial port at least).

My divisions for the "fight" in Africa were loads of 4/1 INF/art and 4 (up to 8) 4/2/3 LARM/MotRArt/Mot. Never attack with the INF, just hold the line and advance if the AI shuffles away.

 

[Culthrasa]

cheers for the replies... finally got it myself. Went 10 marines (6mar, sup art), and only thing i did differently was to wait with naval invasions for about a month after attacking, thereby giving first Portugal then Belgium time to send its troops to Africa. Portugal came dangerously close to my capital had to put in some newbie troops to prevent that...

And yes, Destroyers seem to be better, but they are twice as expensive to build.... Had trouble getting enough naval supremacy on all seazones with subs....