Paradox general design idea, which I like, has been to make France a signficant industrial and military power that is crippled by political infighting and WWI era leadership.

France starts with these friendly "buffs" :)

1) Victors of WWI :

• -75% on Land Doctrine research ("Merde !" as the local says)
  
• -0.3% recruitable population

2) Disjointed government :

• -10% National unity
  
• -0.8/day Political Power

3) Protected by the Maginot line :

• +25% maximum planning
  
• -25% planning speed

Starting National unity is 45% , down to 35% with Disjointed Governemnt.

There's about 260 VP on Metropolitan France, so at game start, France will capitulate if it loses 90 VP., and Paris alone is worth 50 VP.

You also have to deal with two hidden events:
- Losing control of Paris is a "wake up call" that will instantly get rid of all your debuffs
- Losing control of Paris to GERMANY and being already over 70% to Capitulation will trigger "Fall of France" and capitulation

Since losing Paris alone will bring you to 55% Capitulation (50VP of the 90 VP required), it's pretty much instant death.

Also, to add insult to injury, you'll need to deal with Communist strikes before the war that will cripple your industry.

Your first priority is to remove the shacles of "Disjointed Government" and "Victors of WWI" through the National Focus tree.

There's no point in researching Land Doctrine while "Victors" is active, as you already have only 3 research slots.

Victors is removed through Army Reform, but this can only be done if Disjointed Government is removed first.

So right of the bat, go through the Political NF Tree (I'm following a Democratic/Allied Classic path, it works with the alternative histories too, it's even probably easier ).

• Initiate Government Reform
  
• Support Statu Quo
  
• Go with Britain
  
• Strengthen Government Support (One year pause)

This took 4 x 70 days = 280 days

The last one will slowly increase National Unity by 10% over one year, and you can't continue before it's done, so switch to the military track.

Here you have the choice between Defense / Offence.

Defense unlocks a subbranch that allow you to increase forts at your borders, but for now, beeline to army reform:

• Defensive Focus
  
• Infantry Focus
  
• Artillery Focus
  
• Heavy Armor Focus

At this point, you need to wait 85 days for Strengthen Government Support to run its course, so pick one of the Industrial NF.

Once it's done, wait 15 days (Don't worry, Political Power is stored, you're not losing anything) and go back to the political track

• Defensive Stratagems
  
• Army Reform

It's now August 1939 : your National Unity should be at 55% and you can know start to research land doctrine like crazy (and you have 2 x 50% bonus to try to close the gap.

Note : I forgot to add it, but if you uncheck "Historical AI Focus", your chances of survival increase drastically, as the timing of events will likely be off, giving you more time to prepare.

At some point, you'll start a war with the Axis (it's the point of the game, after all):
You need to survive long enough the initial attack until USA join allies and/or Germany get busy with the USSR.

Germany :
Hold the Maginot line , with infantry and artillery, using one of the "old school" generals that have entranchment bonus.
Check Germany NF : when they start researching "Around Maginot", you know they're going to declare against Belgium. If you went defensive, now would be a good time to "Extend Maginot"

Really, the goal is to defend long enough to have time to take out Mussolini;

Italy:
You need to be ready to knock out Italy quickly, so you can worry about a single front.

You need an army of Mountaineers to hold the Alps Frontier .
A few Marines
A few Light tanks and regular /motorized infantry

Your marines should sit in Nice, with their Naval invasion researched well in advance
Tanks and the rest of infantry are also in Nice and other ports, but not part of the invasion.

As soon as Italy joins the war:

• have the mountaineers Attack, drawing the Italians their way.
  
• Park your whole fleet (BB support) in front of an italian port and launch the naval invasion.
  
• Once the port is secure, land the armor and the rest of infantry.
  
• Cut off Italy in two with the infantry going north, to try to cut supply to the one fighting the Mountaineers, while the armor drives down to Roma and others VP.
  
• Prepare another Naval Invasion of Sicily if needed (but the Brits might do it for you).

Soon enough, Italy will surrender: you can then redeploy your mountaineers to the Italy / German border, while armor and infantry need to strategically redeploy to Belgium.

Note about Spain : If Spain is Nationalist, keep a few more mountaineers on that frontier, if they're Republican, your chances just improved a lot as they'll join Comintern.

After this, the war should be easy,

• Do not try to attack through the Siegried line, go through Belgium/Holland once they join the war.
  
• Do not worry about Japan and your colonies.
  
• Keep a small force near Paris at all times, in case some enemy units sneek around.

Once Germany has capitulated, the worst is other, as it will remove the risk of "Fall of France" triggering, even if you lose Paris.

At the Peace Conference, focus on having your neighbours Germany and Italy turned democratic .

They should join the Allies and you can now play a "normal" game without fear of any instant death event.

You can now twiddle your thumbs until 1948 or launch an Anti Comintern crusade. :)

This is not achievement specific, but a good starting point for any France playthrough.
I was inspired to add it following the small discussion in the comments.

If you're new to HOI4 , it is important to not be fooled by the number of divisions any country field. Divisions are administrative units and vary greatly in compositions.

Country A may have 40 Infantry Divisions while Country B only has 10, but if the Division Template of A is 1 Div = 2 Infantry Brigades while 1 Div B = 9 Inf Brigades+2 Artillery Brigades, guess which one is going to plow through the other ?

Additionally , soldiers with no guns are only marginally useful so a division needs its alloted equipment to fight at full strength.

With that in mind, we can look up at the army composition and their requirements in Manpower (MP) and equipment (Inf Eq / Support Eq / Truck / Light Tank / Artillery):

28 x Infantry Div [9 Inf+Support Art] :

• Manpower : 260 400
  
• Infantry Eq : 25 200
  
• Support Eq : 0
  
• Trucks : 0
  
• Light Tanks : 0
  
• Artillery : 672

23 x Colonial Infantry Div [6 Inf] :

• Manpower : 138 000
  
• Infantry Eq : 13 800
  
• Support Eq : 0
  
• Trucks : 0
  
• Light Tanks : 0
  
• Artillery : 0

4 x Alpine Div [12 Mountaineers] :

• Manpower : 48 000
  
• Infantry Eq : 6 720
  
• Support Eq : 0
  
• Trucks : 0
  
• Light Tanks : 0
  
• Artillery : 0

NB : 12 Mountaineers makes it a 24 width division ! This is bad, as battle width are usually multiple of 20. So fighting at 40 width, only one Alpine Div can fight at once. You'll need to spend 10 Army XP to get them down to 10 units and 20 width.

4 x Cavalery Div [4 Cavalry + Recon] :

• Manpower : 27 000
  
• Infantry Eq : 3 120
  
• Support Eq : 60
  
• Trucks : 0
  
• Light Tanks : 0
  
• Artillery : 0

7 x Motorized Div [9 Motorized + Recon+ Support Art] :

• Manpower : 81 200
  
• Infantry Eq : 6 580
  
• Support Eq : 70
  
• Trucks : 3 150
  
• Light Tanks : 0
  
• Artillery : 168

These are actually quite good !

1 x Light Armor Div [2 L. Tank x 4 Motorized + Recon] :

• Manpower : 6 300
  
• Infantry Eq : 440
  
• Support Eq : 10
  
• Trucks : 200
  
• Light Tanks : 120
  
• Artillery : 0

5 x Tank Div [4 L. Tank ] :

• Manpower : 10 000
  
• Infantry Eq : 0
  
• Support Eq : 0
  
• Trucks : 0
  
• Light Tanks : 1200
  
• Artillery : 0

NB : This is not good : with no infantry to "tank" for them (ah ah, I'm killing myself...). A pure armor division is very susceptible to air attacks and will have very low organization . Low org mean they don't fight as long and as often. This particular template as an Org of 10, while the "Light Armor" one has an Org of 40.

Total Army Requirements :

• Manpower : 570 900
  
• Infantry Eq : 55 860
  
• Support Eq : 140
  
• Trucks : 3 350
  
• Light Tanks : 1320
  
• Artillery : 840

Total Initally Available :

• Manpower : 570 900
  
• Infantry Eq : 35 300 [63%]
  
• Support Eq : 106 [76%]
  
• Trucks : 3 350 [100%]
  
• Light Tanks : 1200 [91%]
  
• Artillery : 602 [72%]

So, our infantry is only at ~60% strength and we need to produce 20 k+ Inf Eq. to catch up, the Alpine Div template needs reworking and most of our armor is in a "Glass cannon" Division template. As a bonus, your Manpower is not that great and you're a democracy.

Here is how to quickly get in better shape :

• Step 1 : Disband all Colonial Infantry units. They have no real purpose, since only core territories count for the capitulation meter.
  
• Step 2 : Select the 5 "Brigade de Chars" Divisions and switch them to "Div Légere"
  
• Step 3 : Disband 1 Motoried Division.

Without even unpausing, your total army needs is now :

Total Army Requirements :

• Manpower : 442 800 (-128 k saved)
  
• Infantry Eq :43 320 (-12 k saved)
  
• Support Eq : 180 (+40)
  
• Trucks : 3 900 (+550)
  
• Light Tanks : 720 (-600 !)
  
• Artillery : 816 (-24)

You have less divisions, but they are more efficient, and the infantry is now at ~80% strength.

Focus on producing Infantry eq , support eq, trucks and lots of artillery ( you now have some tanks to spare) and as you gain XP through Focus or Training :

• Get the Alpine Div back to 20 width
  
• Move your Infantry template towards [7 inf x 2 Art + All the support you can ]
  
• Add more tanks to your armor divisions (don't forget to ramp up tank production)