The entire game was a kind of a perfect storm. I had next to no resistance due to constant fighting on the other end. So, after I stomped Arabia and Mayans, I set foot on the other continent, stomped Mongolia and had my ships swing around the back of Beijing and take it from the sea. Venice and Mayans double teamed me but they are pushovers, nobody even came close, and my ships made short work of the Blind Man.
Persia were severely weakened by their war with Russia and China, so Persepolis fell easily, the road was clear and only a handful of muskets was defending. By that time, my Longbows all had Logistics so he didn't stand a chance.
It was then time to take on the Gargantua. All this time, Cathy was free to turtle up, being isolated up north, but constant war with the neighbors and my CS allies spread her out just enough for me to gain the edge. She offered the southern expo for peace, which I accepted, and used new territory to upgrade all cannons to arty.
The fire sale took care of the happiness issues, and I was free to begin one last attack. The longbows served me well in the campaign but they were the meatshields in this siege.
In the end, the suicide charge on Moscow worked, she had the Great Wall, the Brandenburg Gate and possibly Himeji, didn't check. But I completely forgot that Arty has indirect fire, so in setting up for a hill strike, I realized all I needed was an disposable spotter, and luckily I had 3 workers sitting around. Arties made short work of the 88 str city and then not even the Wall could stop a single lone cavalry sentry medic