I'm sure there were many German and Japanese mothers in 1944 begging people to back the war and not let their sons have died in vain too.

It's a very common form of patriotic thinking that is utterly devoid of logic, but heavy on emotion.

Boys die in vain all the time in wars. They do it for reasons that seem to make sense at the time. This causes some bereaved parents to back the war more strongly than before. It causes others (the wiser ones) to come to the conclusion that their sons did indeed die in vain, and that they will not make the mistake of continuing to support foreign wars that are not in the interest of them or their children.

Who you really need to send to the front line in wars is not just the politicians who sent the boys there....but the bankers, businessmen, and financiers who set up and orchestrated the whole thing in the first place and gave the politicians their marching orders. Then it would end right quick. It is those who stand to profit from a war who determine where and when that war shall occur...and how long it will last.