Preturn: We have 13 pikemen, 10 bowmen, 20 MDI and 4 trebs. We have 23 cities to defend.
I think we should attack Umma, which has iron and horses.
(1)560AD: movement.
IBT Germany and Inca start Shakespear.
(2)570AD: more movement.
IBT: Hmm, I guess Sumeria is planning a sneak attack..toward Byzantines! Lots of units move to that city, including several knights. I see a Sumerian galley gets sunk, but don't know by whom. Sumeria starts Smith's.
(3)580AD: Sell a library to make even. Apparently Sumeria is already at war with Byzantines. But those units in our territory will not make it any easier for us..our core will be exposed to the knights.
I try to redirect them to not trespassing our core..
IBT Mongols demand TM and sure. And yes, Byzantine and Sumeria fight.
(4)590AD: I must either have been completely wrong, or the iron at Umma just got depleted. Guess the former..
Umma is on a hill, hmm..not the best kind of target, but it wouldn't matter.
Still too many units around it, so wait.
Have to sell another temple.
IBT we finish a market and now have +3gpt.
(5)600AD: Sumeria completes Shakespear and starts Newton. I guess it has no saltpeter as I do not see any musketmen or cavalry.
(6)610AD: I ask Sumeria to leave and it actually does so! This sucks. Too many units at the border and if I declare it's surely a suicide. I can count totally 49 units.
No way we can win it. OK I'll just take Umma and call it a virtual victory. However there is one big stack next to it so I'll let it step into our territory first.
(7)620AD: I decide to wait one more turn.
IBT we complete FP.
(8)630AD: I demand Gunpowder from Sumeria to make it furious and ask it to leave, and it declares.
Our payment is also back so we are making +22gpt.
Some towns are definitely going to fall so I sell all improvements, and gift to Zulu.
MDI retreats a knight and a bowman kills it, and we enter GA.
I establish embassy with Byzantines and sign RoP. It's at war with Mongols too.
Our stack of 14 MDI, 3 pike, 5 trebs are next to Umma.
IBT the RoP pays as Byz longbow kills a knight for us. Apparently Sumeria is already at war with Zulus so it took all the gifted towns except one.

Sumeria razed Uruk and captured Carchemish.
(9)640AD: trebs take one hp off each of the 3 pikes in Umma, we lost two MDI and raze it! We get 7 slaves and a treb.
We kill two knights and an MDI in our territory.
I gift another town to Japan. We are making +130gpt so I buy Gunpowder from Mongols by WM+48gpt+15g. Mongols are likely to MA with Sumeria as it's at war with Byzantine too.
And we do have saltpeter at the border. I upgrade one pike.
We can even make a 2-fer! I buy Chemistry from Germany by 66gpt+WM. Chemistry can get us Astronomy or Chivalry from Zulu but not both. I go for Astronomy as we do not have horses (oh we do have, after razing Umma) and knights are too expensive for us. And it doesn't matter anyway.
I loan 162g from Byzantines and pay 9gpt, and upgrade two more pikes. We have 3g with +4gpt.
IBT Japan declares on Byzantines, and we lose no towns!
(10)650AD:
I keep most units unmoved, including our stack at ex-Umma. You can choose to move to Sumer, but it's size-13 and will be very tough to get. So we probably just want to move it south to take back Carchemish and Eulbar. Or you can go for Sumer.
Zamua will fall next turn as there are probably 30 units around it. I'd probably move units from both Zamua and Nimud into Samarra and gift Zamua to Japan.
Izibia will probably fall too soon, but we can gift to Inca (Japan is at war with Byzantine and Izilia is too close to Byz).
Our north is probably OK except some pillaging. All Sumerian attack force is at south.
I'm glad I'm done with my turns. Heck, I even got 3 techs.

I could have saved the gold to rush units, but I'd rather see us die sooner. You'd better not make peace.
Now good luck with this hot potato.