You’re missing an important point. The bottom level soldiers don’t decide to go to war. The king decides to go to war. Behind every form of government there is a supporting group, in the case of the Greeks, it was the heroes. The supporters of King Menelaus, the heroes decided to support the king’s war with Troy. The supporters have a lot of reasons to follow king Menelaus to war. First there is the loyalty to the king. That’s a do or die situation. To stand alone and not support the king is basically an act of treason — pretty much a no-brainer. In addition to not supporting your king, is robbing . . . or earning the spoils of war from the Trojans. So for the heroes it’s a win-win or perhaps lose everything choice.
This would be a fun writing prompt on reddit writing prompts. Here’s how I think a war would be waged. First off the president can’t declare war, nor even wage outright war beyond a certain number of days with out the approval of the Senate. Canada is a pretty small country with a lot of vulnerabilities to the US. There would be no reason to actually go to hostilities with Canada other than to punish Trudeau. Albeit Canada would have the backing of the rest of the British empire . . . they’re another set of weaklings. There’s not much the world’s 57'th largest military could do to stop the largest military — But back to the war. The strikes and saboteurs would cut off all of Canada’s communications and electricity, strikes would take out all of Canada’s 30 naval vessels, blockade all 3 Canadian naval ports. Crater all of Canada’s 8 air force runways and destroy all 77 Canadian assault capable aircraft. Drive up highway 87 about 20 miles, and grab that wayward skag. I may be wrong, all of this could happen in about . . . two hours.