OTOH, if you commit a behemoth like Austria-Hungary where 40 per cent of the country belongs to disadvantaged minority ethnicities and then you lose the war and the population is reduced to digging roots from the ground and making soups out of leather boots (I am not exaggerating), there isn't any reason to continue the existence of such a structure left. Only fear that the uprising may get you killed, but if the soldiers are demoralized too, they won't shoot.
On the contrary it looks like democracies have a hard time even deciding to defend themselves, because people will never decide risk a war on their country. And Putin is exploiting just this, IMO.
But many important Western European countries were at least flawed democracies since approximately the last quarter of the 19th century. For example, Italy was a democracy when it launched an abortive attempt to conquer Ethiopia in 1896.
Iraq did a bit better in that respect, but it isn't a new Japan.
This just brought to mind the idea that it's remarkable that America has weathered at least one and possibly three (depending on the definition of success) lost wars in the past 50 years without severe political consequences: Vietnam, Iraq, and Afghanistan. It wasn't without consequence but it did not cause anything like Russia in 1917 or Germany in the 1930s. The worst we got was a shirtless jackass wearing horns on the Senate podium.