The really big tech? Why Engineering of course, unlocking my Citadels. My production cities had all build walls and would start on citadels as soon as possible. Right around this time, Zara decided to get cute and used his EPs against me. How did I know that he did it ... because I went back to the turn before and compared EPs. The BUG mod is working on putting this information into the Espionage Screen.
That dastardly deed really sealed his fate ...
While that army matched North, quickly followed by other siege units and knights, Monty was back to going after Mansa. I didn't particularly like some of Zara's city placements so a few cities got razed and replaced with (in my mind) better (and more) cities. Zara had captured a lone barbarian city that was miles away from his capital, so after taking his capital, I had the chance to pointy-stick tech - picking up gunpowder in the peace deal. I immediately sent enough units off to kill that remaining city - 10 turns should be enough to get them there.
My warring had slowed my tech progression, but I was still in the lead enough to land Liberalism (taking Nationalism). Knocking off the Taj Mahal and burning a Great Prophet on my first single person Golden Age gave me 24 wonderful turns to regain the technological lead. That plan didn't turn out that well as I landed Military Tradition and unlocked my Unique Unit (Conquistador). Also, Monty was distracted trying to regain Timbuktu (again) ...
And so the Monty-back-stab started with me chewing through cities from the West while he was engaged against Mansa in the East. I certainly put his ivory to good use. I took over half of his holding and then asked for a break ...
Timbuktu was a very small little city (size 1), totally crushed by Mansa's culture, but it was the Hindu holy city and pulling 68g per turn. A very nice little pickup. During the Monty War # 1, I also knocked off Zara's ex-barbarian city - so he was no more. I had also started to dial up my espionage slider, running at 70%. This allowed me to gain city visibility on all the other leaders. It also allowed me to pick up some critical techs from various leaders ...
Monty war #2 finished Monty off. I even bribed Mansa back into the deal against Monty. This did two things - distracted Monty and killed some of Mansa's units, allowing me to roll straight from finishing Monty off to taking out Mansa. I burnt some of my Mansa EPs to revolt one of his final cities so that my 2 mover cavalry could roll straight in without the need of siege weapons.
At this point, I could have kept on rolling on the military front, but I've done that too many times. I decided to set my eyes on space.