earth and everything in it is temporary.
Heaven and Hell are permanent.
War is the the product of choices made.
There are agressors and victims.
No one knows how many souls involved in war are won or lost.
But we do know that God longs for all souls to return to Him - enough so to come down to earth as man and to die in order to make way for souls to join Him.
Jesus did not come to end earthly wars. He could have, He didn’t. In fact, He knew Christians would be slaughtered in His name. He spent His time here revealing His Father to us and calling us to keep our eye on the prize.
So, obviously, one lost soul is worse than war on earth.