Is there a different way to win a war than sending troops and artillery?
There is: Do it the subtle way. Destroy the infrastructure, by selling and privatizing, to let your opponent pay off debts that actually don't exist. Erase the ability to do self-catering with home-grown food, introduce the dependence on imports. Carry technology and patents out of the country. If human intelligentsia can't be lured away, make sure they can't make any profit out of their knowledge anymore - forbid them to work in their disciplines, declare graduations and diplomas to be invalid. Abolish law and order and take your sweet time to install yours as the new ones - to let chaos move in, and crime take hold. Additionally, send your own criminals in to fool the masses and to let the daily terror on the streets be perfect. Pump your own wares and goods into the newly acquired territory - to calm down the conquered masses and to make profit yourself; best even is if you let it be accompanied by advertising and propaganda how good it is, how grateful people can be to have it, meanwhile you can do the dirty work to strip them off their assets. While being at the assets: Rearrange the overall property situation. If the pattern makes sense or not, it doesn't matter - the confusion and the gain for your own fraction is the main objective.
At the end of it all, most importantly: Break the morale, the mindset of the people that you annex. Deconstruct the education system and build it anew. Let culture disappear to be never seen again. Kill the spirit of what made these people up! Make sure that way that you're going to be happy with your annexion for the coming decades - 'cause the resistance fades away with the people aging.

War techniques change from army to structural war.
No area is restricted anymore.
From finances to markets to people to food to supply to natural resources, even to patents and to environmental standards, as well as known corruption, doping, tax evasion, known connections, drug traffic, weapon sales, international fraud - all of these territories have been approved to be used to cause another fraction damage which doesn't follow the desired order.
The ones fought on shall not realize what's going on until they're very much drowning in the soup. They shall be kept at a state until it's too late to notice. And, even if they understand whose fire they're under, they shall be kept too helpless to practically do anything against the scattered fire they've been put on.
Let them sleep until they've been surrounded and until they realize there are too many fronts to deal with at one time.

If negotiations demand the impossible of you, then you know: They want war.
They're not simply dumb, they act on purpose.

Make them believe the grass is greener on our side.
Make them believe our media tell the truth and theirs is lying all the time.

There's not always a need for soldiers and tanks.
Sound out all of your options.

Crisis in the motherland leads to freedom for its colonies.

Occupied land is a good servant.
Never let it slip off your hand.

Split and devide.
Let your enemy bash himself in, or at least weaken his military power by splitting his land into pieces.

Report the death of a leader and you have a chance of demoralizing his troops.