Let’s say the US and Canada agreed to settle all disputes, all at once, in a contest of wits, sprung upon a unexpecting Maine (US) and Nova Scotia (Canada)- they will fight to the death, whoever manages to conquer the other, the larger losing country forfeits all national claims to border and national issues, and everyone in the conquered state/province will be put to death by a joint Canadian-US task force- so there is incentive to fight.
Full military and naval blockade, with NATO, Chinese, Russian, and hell, Cuban and whoever else wants to join in, full militaries blocking Maine and Nova Scotia. Neither state/province is warned in advance, nor given any indication what is happening. They are warned by radio broadcast only what the rules are once per day, rest of the time, airwaves are jammed. Neither can import, only use what they have resource wise.
In case pacifism overtakes them, a daily drone strike will bomb a household per day, with a promise to double it each day.
Day 1, 1 house destroyed
Day 2, 2
Day 3, 4
Day 4, 8
Day 5, 16
Day 6, 32
Day 7, 64
Day 8, 128
Day 9, 256
Day 10, 562
Day 11, 1,124
Day 12, 2,248
Day 13, 4,498
Day 14, 8,996
Day 15, 17,992 homes destroyed
We will only stop on days we can observe large troop movements fighting. If you don’t want your families destroyed indoors, you fight in the field. That should solve the pacifism problem real quick. Anyone trying to escape gets shot. Anyone attacking the quarantine forces gets shot. Anyone protesting in front of the quarantine forces gets shot. Only thing that matters, if a fight to the death between Nova Scotia, and Maine.
Who would win, and how? What resources would they use, who would conquer what? What would the war look like?