should we bring back national sevice ?

No! National Service is just a fancy way of saying Conscription, and we are fast to criticise countries that have that in place. People should not be forced to join an armed service against their will, even in a state of world war. A better alternative to National Service would be a system of voluntary work for the local community, something of actual benefit that would hopefully make them proud of their town or city, even if it was just work in a charity shop or cleaning graffiti.