Are there international or other laws you care to stick to?

I fired my legal team when I was elected to my high office. Nobody told me about any international treaties. If I don't know about them, they don't apply, right?

Does your populace care about active duty suicides?

@Lumberjack, interesting, had not considered. I guess it could get messy that way. Maybe screen our operators for high sociopathic tendencies, and otherwise generally outsource to, uh, friendly nations?

So ... "How can I effectively nuke the city without actually nuking the city?"

@RBarryYoung, I said no such thing! The media (that I own) are distorting my words ... But, if there were a way...

If your "no nukes" rule really is just about nukes, then conventional explosives can level the city within your budget (although depending what you mean by "dug-in" that might not actually take out all the defenders). If it's really about that being a boring solution, maybe you could elaborate what kind of non-flat condition you need the city to be in afterwards? One approach would be to bust the bunkers, accepting the damage that does on the basis that half a city is enough. But is it?

Do you want the city itself to remain physically intact(ish), so that it can easily be repopulated by your guys, or are you happy for it to be flattened if need be?

City? What city? There was a city there? I don't know of any city. But if we're talking cities, we'll build a great, huge city. We build the best cities. It will be glorious.

Have you got time and encirclement enough for a siege?

@pjc50 With a trillion bucks, mercs, home troops, planes, toys, tanks, drones, artillery ... uh, yeah, I hope we can encircle a city.

I'm sure it's just coincidence that Oppela backwards is Aleppo...

Can't we just pay them to leave with some of that trillion?

Is cyber-warfare an option?

All options are on the table.

Nice try, Vladimir - we're not giving you any new ideas.

Are my citizens squeamish about protecting any mercenaries I hire?

I'm rather surprised that no one has mentioned a Neutron Bomb, does this fit into your requirements? This is exactly the situation these weapons were designed for and your allergic reaction would merely be acute as the traditional radiation effects do not linger.

I prescribe a few neutron bombs and a couple cases of antihistamine for your allergies, and some caffeine to balance out the drowsiness induced by the antihistamines. Edit: oops, @MatthewPeters beat me to it.

@aroth, I thought you were a pharmacist backing up my recommendation lol

At first glance this was an interesting question, but since you don't specify anything about the expected result (do you expect the city to be used by your own people afterwards, how much time do you have for the actual operation, etc.) it's just a guesswork... too open.

Just give everyone a smart phone. They won't notice anything you do after that, as long as the news doesn't report on it.

@AnoE, yes, the goal is to have a (new?) city there afterwards, with a more freedom-loving population, hearts and minds won, etc. Timeline should be realistic (I don't expect wonders in an hour, but can't wait years either).

How close to zero are we looking here? Single digits? Double digits?

If you determined that everyone in the city is an enemy combatant or something, what keeps you from levelling the whole city with conventional artillery and/or air strikes (drones to be safe)? Sure, some may survive in some tunnels, but what for and for how long with everything around them shelled to dust?

Unless you can rapidly prevent all civilians leaving and being able to travel globally. You may experience a home front terrorism issue.If you kill millions of peoples families you will radicalise huge numbers. Depending on cultural issues they may or may not be willing to launch suicide attacks but many would likely be will to take huge risks to a carry out revenge attacks. Also do you fully control your own population - depending on your tactics you may radicalise elements of your own population. So you need a plan to prevent asymmetric warfare on the home front

@GraemeMiller, that is a great comment! I would love to see it turned into an answer.

@SerbanTanasa Quick answer added - hopefully a different perspective as I just can't see any enemy just sitting and waiting to be crushed :)

@SerbanTanasa I've noticed a lot of answers on here that use the entire trillion dollar defense budget just to take over this one city. It seems like you're looking for a realistic answer here, and no country would realistically spend its entire military budget on a single city. Maybe it would help to give a ballpark of how much of the trillion you're willing to spend on this operation? Although I do enjoy the creative answers like shelling the city with a hundred trillion pennies :)

You may wish to study the Setats Detinu military, which already takes very few casualties wherever it goes...but has difficulty keeping territory once taken.

@SerbanTanasa you've answered some questions here in comments; please consider editing clarifications into your question. Thanks.