In a defensive war - there is no vote whether or not to go to war. You are immediately at war because you have been invaded.
War, real war - and not just bombing random countries with little to no anti-air defense and then huddling up in microscopic and ultra-defended zones while waving a 'victory' banner while having undisputed control over near 0% of the country, is a slow grueling, and bloody thing. This is how you end up with things like both the USSR and USA losing to Afghanistan, Russia losing to Chechnya, USA losing to Vietnam, and so on endlessly.