Did you have a causa belli against them?
Nope. I just ate the -2 Stab, War decked they heathen butts, and with 8/4/2 (Level 2 Defensive and MilTrad around 75% I think) drove them to 100% warscore. Then I annexed them fully, and Europe didn't even blink!
Supposedly I was gonna get something like -7 AE with several neighbors (Aragon [whom Castille and I have had for lunch already, thus the good Military Tradition], Castille, etc.). But when I look at them in Coalition map, I only see some AE with Savoy, probably because of a Claim I fabricated on Nice some years back. Here I'll grab a few more screen caps.
BTW, this is with a few mods: my HYW Historical 1444 Start mod; Cores never expire; Improve Monarch; Rebalanced Buildings; No Comets. I don't think any of those mods were at all necessary to pull this off though. The HYW one definitely helps France by not requiring an invasion of Britain to get them kicked off the contient (except Calais) but other than that, most of those have been irrelevant to my playthrough so far.
I'll grab some more screen caps. I took Exploration first thing. In hindsight, that wasn't really necessary. Until you have Diplomacy Tech around at least 7 (in fact 9 is necessary to colonize the far NE of Canada even with basing from Iceland) Exploration is not really doing anything for you as far as I can tell. Would be fine to take something else first like Defensive or whatever. I took Defensive second, but have been neglecting it a bit to stay up with Mil Techs. The AI in Europe loves to go fast through the MilTechs.
ADDIT: yep, miltrad is 75.4. Hopefully this massive annexation doesn't wreck my economy. I'm bleeding about -19 per month and I've already got about 7 loans. Time to fire some advisors I think.
The coalition map. Only AE that shows is Savoy with -3
Here is the Conquistador Battalion that handled the job
Apart from finishing HYW, I like to very quickly get into a war for Girona and then force Aragon to give Rousillon to Foix. Then when I annex Foix I get two for the price of one. After that, War on Guyenne and Provence. Then a followup war for Barcelona. In this case Castille had already annexed it from Aragon.
Here is 1475, a few months before I got Castille and Portugal to 100% WS and took Barcelona (as well as forcing release of Galicia and Granada). I find that crippling Castille is a good move.
I don't know what people are smoking when they claim you cannot be a warmonger in this game. So far I have been in the following wars:
1. HYW (with my mod Guyenne is owned by ENG but Normandy is just occupied) ~50%WS -> Release Guyene = 0 AE
2. Conquest of Provence 100%WS -> Cede Provence, Release Bar (cash, trade power, etc.) ~ 7AE which virtually disappears within two years. Immediately make Bar a vassal.
3. Conquest of Barcelona 100%WS -> Cede Barcelona (plus cash, trade power, annulments, etc.) ~ 11AE
4. Annex Foix (vassal) + Rousillon
5. Conquest of Arnor 100%WS -> Release Provence (they had taken Anjou and Maine while I was busy with Aragon), Cede Maine, give me all your lunch money, all your base are mine . . . and I'll back again in five years to take some more . . . *Leave Brittany ALONE!*
6. Conquest of Gascogne (vs. Guyenne) 100%WS -> Full Annexation ~14AE or thereabouts
7. Conquest of Barcelona -> 100%WS on Portugal -> give me some cash, and stuff, and I want a lifetime supply of Nandos . . .
100%WS on Castille -> Release Galicia, Release Granada, Cede Barcelona, plus some other stuff . . . see you in five years Pepe!
8. Conquest of Anjou -> 100%WS Cede Anjou, etc., etc.
9. Annexation of Aztecs
So its 1495, and I've already been in 8+ wars, all of which added at least one province to my Empire (the Aztec thing is just an insane amount of land . . . thank God those things don't count against overextension or I'd be done).