Since the invention of the airplane and the use of them to drop bombs, I think the idea of the "just war" has become obsolete. With the use nuclear and hydrogen bombs, the concept of a "just war" is now a total absurdity, we're speaking about the indiscriminate mass murder of millions of non-combatants, not to mention we may be wiping out the best genetic strains of the species.
A full nuclear war between Russia and the U.S. would probably kill around 200 million human beings, and make life unbearable for the living. After a thermonuclear exchange our atmosphere, climate and agriculture - on a global scale - will be deeply altered, every city that was hit will have no electricity, no running water, no police, no firefighters, and, most likely, gangs of armed thugs roaming the streets breaking into homes, killing the occupants and stealing whatever food there is to steal.
The manufacture of nuclear weapons ought to be classified as a crime against creation, for that is what they are. Any person who authorizes the use of these hideous devices will become the biggest mass-murderer in the history of our species. If nation-states and those wannabe nation-states cannot learn to solve their problems without violence, our species is doomed.