Oledavy, rho21 did a nice job of pasting in the city defensive strength formula. I think it makes sense overall, but if I could make a small change, I think I'd alter it so that the global bonus isn't quite so high. It would make more sense if the base strength was something like HALF the combat rating of your strongest unit, not the unit's strength -10. Then there would be more incentive to keep strong melee units inside cities to increase their defensive power. I think it's a little bit silly that building a single unit can magically increase the strength of every single city on the map by a giant amount. Anyway, that's the formula in the base game and it's important to make decisions around those numbers. RFS-81: it's strongest unit ever producted, not strongest existing unit. I also think it should be the strongest unit you currently have, since that would reward players for having a powerful current military, not building a single one-off unit and not having to worry about things ever again.
Athmos: I've thought about using Professional Army policy that unlocks from Mercenaries civic as well. However, I'm not sure that I have the policy slot available to use it! I absolutely need to keep running Conscription in the Military slot or I will go bankrupt. That leaves the Wildcard slot, and at the moment I'm getting a lot of use out of the Bastion policy there to beef up the defenses at Aquileia. Perhaps this will change in 5 turns, and it certainly would be nice to upgrade both of my remaining warriors to legions instead of only one of them. We'll just have to see what conditions on the ground look like in a few turns.
I spent a lot of time thinking about this game last night, including not sleeping especially well. My mind always gravitates towards worst-case scenarios and I couldn't help but keep pouring over all the bad things that teh could have lurking out there in the fog. What if he was about to spring horseman on me? What if he built some battering rams to take out the city walls? Battering rams have no power rating and therefore don't show up in power tracking Demographics. There were a lot of ways that this could go wrong for me. So it was with some trepidation that I downloaded the save this morning and took a look:
Yuris, you magnificent bastard!

The player who's been seemingly sleepwalking through this game to date decided to jump into the war on my side. Look at Frankfurt, which has lost about 70% of its health and seems likely to fall next turn. That must be where the Aztec forces are concentrated (I have Yuris written down with 3 Eagle Warriors and 2 archers total). Very nicely done, Yuris. The weakness of teh's archer-heavy force is glaringly obvious here. Because teh has built nothing but slingers/archers all game, his cities are still stuck with the default city strength of 10, and as you saw up in northern Rome, that makes cities a punching bag for any kind of attack. I think teh might have been stuck in the Single Player mindset, where the AI is clueless and stacking up a bunch of ranged units is the path of success. That doesn't work in Multiplayer; you need at least a few melee units to protect the ranged units and strengthen your city defenses. Long story short: teh launched an attack on me without protecting his own flank, and it looks like he's going to pay the price.
From a metagaming perspective, this is probably the best move that Yuris could make. Yuris is critically short of territory; he is sitting on 4 cities right now and zero room for further expansion through peaceful means. He must take over land from someone in order to remain competitive, and teh was the only realistic option due to the placement of Frankfurt. So from Yuris' seat, this is likely his best chance to become a major power. However, it's also undeniable that this attack heavily swings the larger picture in my favor. Teh's attack was the only thing that threatened my ability to finish conquering northern Rome and running away as the game's superpower. By plowing into teh, Yuris relives most of the pressure on my civ. In other words, this makes it more likely that Yuris will finish second, but it also makes it MUCH more likely that I'll finish first. Some people would approve of this as making the most of his position; after all, why is Yuris under an obligation to help teh stop me from winning the game? Other people would say that anything other than finishing first makes you a loser, and would condemn this move. I'll let the lurkers debate the merits of this in the lurker thread, I'm just happy to take advantage of it.
Let's see if we can help out Yuris a bit:
I noticed that the injured German archer from last turn had disappeared. Did teh retreat it back into the fog, or did the archer from Vilnius finish it off? I hope it was the latter case, no way to tell right now though. Teh also used one archer to pillage my horses (for 50 gold - we saw that move last turn!) and moved up his warrior next to the city itself. The warrior is pretty much irrelevant; teh is still running Classical Republic government, not Oligarchy, and if the warrior tries to attack the city it will deal very little damage while injuring itself heavily in the process. One warrior can't put a city under siege, and I could ignore the unit for now.
Instead, I planned to target the archers to stop them from continuing to shoot at Aquielia. The city walls fired first and did 56 damage, leading to this archer vs archer combat that I moused over. I mentioned last turn that the city walls along with my archer should be able to kill one of teh's archers in combination, and that proved to hold true. Chalk up one dead unit for teh. Also note the damaged unit penalty: units lose 1 point of strength for every 10% of their health that's missing, and this turns out to be a big deal indeed. 25 strength against 9 strength was a massacre here. (Why did I attack the southernmost archer? That allows teh to send the northern ones against Yuris if he wants, while the southernmost archer really had no one to attack other than me. I figured that I might as well facilitate combat between teh and Yuris if they want to fight each other.)
Here's the overview of this combat theatre after moving all my units. Teh's invasion force is looking a lot less scary this turn than it did last turn. I'm continuing to hold my full-strength warrior just out of archer range; if teh's warrior heads any further west, I'll be in position to attack it. There's an archer at 86 HP that I'm also moving over from Arretium, where I believe it's more important to move over to Aquielia a turn faster rather than wait to heal to complete health. The injured warrior and slinger are moving over to Arretium for a safe place to recover. Thank goodness I had the foresight to get that road between the two cities and speed up the transit time of units shuffling back and forth.
Next, the front in northern Rome:
Lugdunum was the target for attack this time, with three legions and the horseman in position to make the assault. I screenshotted each of those combats and pasted them together here, going through the three legions one at a time and then ending with the horseman. I came up just short of being able to take the city in three attacks from the legions. I'll also emphasize again the massive difference that the Great General + Oligarchy combination makes here. At strength 40 against strength 30, this would be a difficult and grinding siege that would last multiple turns. Without legions, it would be strength 36 against strength 30, barely an advantage at all. It's only by stacking together the legion + Great General + Oligarchy combination that this becomes something approaching routine. Even the horseman has a bit of a tricky fight against the crippled city, since it's only 36 strength and doesn't get the Oligarchy bonus since it's not a melee unit. For all that we talk about how melee units can be underpowered in Civ6, this is their specific power role: sieging and capturing cities.
This is the overview in the north after moving all of the units up here. I moved the Great General over to buff the western legion and give it a third movement point next turn. The units at Lugdunum will need to heal for one turn, but that one turn of rest should get them all back up to full, then my five units can start pushing on Mediolanum together. Constantinople finished repairing its monument, and I've set it to a Commercial district for lack of other things to build. Nothing much is going to get constructed here until after the war is over and I can end the occupation penalty. (These cities don't even show up on the trade screen as belonging to me; they are still considered TheArchduke's cities until he concedes them or is eliminated. It's a bit silly.)
At Ravenna, I cleared a rainforest tile where the Bath district is going to be placed in 2 turns. The production bonus knocked out most of an archer, and I'll be able to complete it and then immediately start on the Bath district afterwards. The food bonus from clearing the jungle didn't appear on the interface, which I suspect is another buggy result. The fact that Ravenna is currently over the housing cap isn't supposed to affect that free food from the jungle clearing; at least it didn't have any effect in previous patches. My guess is that the food box will update correctly at the start of next turn. Also check out which tile is going to be claimed next by Ravenna: the jungle tile northeast of the bananas. Perfect!

That will open up the Feudalism farming triangle with the two floodplains tiles controlled by Arretium. This builder still has 4 charges left, and so I'll farm the floodplains next turn, then clear and farm the jungle tile over the two following turns, funneling the jungle clear food into Arretium (which can make better use of it). Then I just need to construct the Bath districts at these two cities and housing won't be a problem for a very long time. The city development is working almost perfectly here.
Finally, the overview of my southern Roman core. Yuris appears to be retreating with his Eagle Warrior, and I seriously doubt he wants to pick a fight with me now. That's a relief. After this current round of military builds, I will likely be safe enough to go back onto infrastructure. Hopefully the front with teh is stabilizing now; let's continue to defend over there and start getting Baths and Commercial districts up and running elsewhere. I won't make any attempt to push into teh's territory; I'm happy to keep conquering northern Rome and let teh fight it out with Yuris for a very long time.