Related question: How can I stop the Assassins' influence go lower over time?
Is there a way to keep 100% all the time?

What I've been doing is training up my assassins and then assigning them to the cities. There should be an option for that when you hover over a city on the map. It's a slow process though.

I've got a city stuck 'Under Siege' -- no matter how many times I do the mission, it never reverts back to Assassin control... has this happened to anybody else, and does it clear up?

Hm that sounds kinda weird. Do you have all the other cities under your control? Are you sending your assassins there right away after you do the defend the city mission? You need to send them on missions to gain control of the city and keep it. If you're going back immediately and it's still under siege it might just be a glitch... worst case scenario, you have to do another playthrough. Sorry, other than going back immediately to keep control of it, I've got nothing. Maybe someone else knows.

Just As A Side Note I Think It Excludes Rhodes Just To Be Nice... As To Unlock Rhodes You Have To Play Certain Multiplayer Maps.

Thanks for that, I was wondering what the deal was with excluding one city. Seemed silly to me. Good to know :)

is it necessary to do all of the missions for each city, or just chose the Reclaim City one?

You don't have to do all the missions, as more will keep popping up over time. It's good to do a couple though and increase the assassin's control of the city. That way, when you do reclaim the city it will take longer before the templars try and take it back (when the city is under siege), leaving more time for you to get all the cities under your control at once. I would suggest doing a few at the very least.

thanks Galenhithwen, once you have a city is it better to do the rebuilding ones or just go for the high xp ones?

Well if I remember correctly, the building ones require a monetary contribution from Ezio (which you might want to avoid if you're saving up to get the 'sage' achievement). I personally went for the high XP ones to level up my assassin's as fast as possible. I don't think it really matters though. It's all preference. If you want to gain fast control of cities though, try to do missions that yield a high assassin control percentage. Good luck :)

you don't need to defend your cities to get the achievement, i had more than the half of the map under siege and i still get the achievements, you can edit it?

I believe the reason for Rhodes being left out is because throughout time Rhodes was never defeated and eventually became a neutral area.

Rhodes isn't available unless you've unlocked it in multiplayer. They probably left it off so this achievement can be completed without Xbox gold.

nyllon is right

For some reason, I can't seem to go beyond 50%. Once I reach 50%, I start a couple of high-conquest missions, but once I finish them, It's still 50%. Do I have to try harder, am I doing something wrong, or is it a glitch of somesort? :O

For some reason, I can't seem to go beyond 50%. Once I reach 50%, I start a couple of high-conquest missions, but once I finish them, It's still 50%. Do I have to try harder, am I doing something wrong, or is it a glitch of somesort? :O

Not entirely sure, but sounds sort of like a glitch to me. I'd keep trying though, just make sure that you keep on the quests that pop up and don't leave them sitting for too long. If that still doesn't work then you might have to get it in another playthrough. The 'clowning around' achievement in brotherhood glitched for me in my first playthrough so I had to do another playthrough to get it. Sometimes it's just a stupid bug... if that's the case then I'm sorry dude :| Good luck.

I have the same issue as eightdivines in that none of the cities I capture will raise above 50% Assassin's control. However this has not prevented me from capturing any other cities and I have half of them removed from the Templars. I just thought it was odd that the percentage will not raise to over half. Perhaps you have to be at a particular memory in game? I'm only on Memory 4 or 5.

It's been so long since I played that I don't remember if I was in any particular sequence when I got the percentage up. Wish I could be more helpful :| If you keep playing and find that it starts working in a particular sequence let me know and I can update my solution for others with the same problem. Or if you find anything that fixes it. Again, sorry I can't be more helpful, haven't heard of any way to fix it yet...

I'm not really sure, but to me it looked like you have do build Assassin Dens in the cities and then assign more Assassins to them for the percentage to go up. I was only able to reach 100% with a city after I built all 4 Dens and assigned 5 Assassins to a certain city.

Even then the percentage goes down though. I only realised for the first time last night that once you've assigned assassins to a city, they can still actually do missions within that city, meaning you can have missions underway constantly in every city you control. For ages I've been sending out my normal recruits to these without realising!

Once you choose a mission, press "X" to switch to the assassins that are in that city to allocate them to the mission instead. You can also mix and match between city assassins and your regular ones.

Nice tips didn't know that thanks Obi

AWESOME tip about sending the assassins within each city to do that city's missions instead of sending your at-home assassins. This helps.