I've been playing a campaign as the Spanish on hard. I must have tried about 6 crusades so far, year 1201. Four of them have been successful, Egypt, Antioch, Syria, and Naples. My Genoa crusade was really weird. I sent Inquisitors out ahead of my route after the Pope excommunicated the Italians to whip up the zeal. The route was very short,but when I was one territory away from Genoa, Provence I believe, I get this message that Genoa has been returned to Christian hands and your crusade has been disbanded. The Germans held Provence and offered to ransom me back my army, with my level 7 general and heir for 3000 florins lol. My other loser crusade just wandered around central Europe till my army wasted away to nothing.
My last crusade however was my best to date.
The Sicilians were excommunicated and the French and I had a race to Naples on crusade.
I arrived by sea in one turn and so did the French. I had to defeat the French first, my 1200 vs his 1500. The 550 Sicilians watched us duke it out, then I had to attack him with my tired troops. My 2 units of Santiago Knights carried the day. I had kept them in reserve during my battle with the French. I sent them behind the Sicilians, who were camped on a hill, engaged them from the front with my tired men at arms and spearmen, and charged them from behind with those Knights. The Sicilians put up a great fight, but they broke and ran when those 80 beautiful Knights slammed into them from behind. The Pope appreciated it so much, he broke his treaty with the French to remain my ally. Nobody stops a Spanish Inquisition!

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Diplomacy is the art of telling someone to go to hell so that they look forward to making the trip.