I launch a surprise attack, which takes Toledo and Valencia - and France has Pamplona, so Spain has no castles... and they are as broke as me - it looks bad for Spain, but the Pope steps-in... I can't attack or I'll be excommunicated. Never mind, I put out some bait for the arrogant Spanish... a prince:
Pleasingly, he attacks - and from two directions, but I have placed my army at the foot of a mountain - I should have a good defensive positon:
The enemy must climb a cliff to get me - under cannon and musket-fire!
He has good units... but badly combined - the first army is all infantry, the second cavalry and missiles - I deal with all comers by pike-and-shot.
They leave a trail of bodies all the way down the mountain... knowing that Spain is broke, I ransom the prisoners

(this line of the family is traditionally chivalrous, but there is no way I'll let that many enemies go to reinforce the other five stacks around Leon...)
Bad news for Spain next turn:
The Pope dies! And I kinda own the Papacy! And the new Pope is a warmonger! The crown-prince wastes no time, and moves on Valladolid - he finds it well-defended:
I cannot afford to waste time... my armies are plagued, and losing strength with every turn... I have no money to recruit any more or retrain - prince Fernam is inexperienced, but naturally talented, I attack the enemy in the field hoping to destroy them all in one swoop.
Heavily outnumbered, in cavalry Spain's advantage is 6:1... I begin to worry about now! Those pike formations look a little thin...
It is one of the most savage battles I've fought... led by their chivalrous prince, they don't wanna rout easily. Their cavalry mops-up most of my muskets, but my brave Aventuros prevail over the charging cavalry in the end...
Over at Leon I use one army to seige the city, while sneeking another around behind to take-out the armies on the bridge so they can't reinforce their king:
Led by my best and most dreaded general (mighty Theodosio of the notorious Soarez family, in possesion of the 'ark of the covenant'), it is a cake-walk. Spain is now reduced to two stacks and one plagued city, and their king decides to make a glorious exit from the game during his next turn:
To say I have a strong position is an understatement:
It is a total massacre... for good measure I execute the prisoners, and the once mighty Spanish armies are reduced to a mere 16 troops fleeing in terror... Leon is taken next turn, and that is that.
As well as destroying Spain, I sack a half-dozen other cities around the world. Malta is given to the Pope, I marry my prince to a pretty Russian princess (who are vassals of my ex-allies Norway... I have promised to free her people and restore them to glory!) and give them one of my citadels - with all my plundering in the last few turns my finances look better, and my most prosperous cities are healthy again... but what is this I see? What are those treacherous Scots up to?!