As a Holocaust survivor, commenting on the lessons of WWII, said:

‘When somebody says they want to kill you, you should believe them.’

To remain at peace when you should be going to war may be often very dangerous. The tyrant city… is a standing menace to all…. Let us attack and subdue her, that we may ourselves live safely for the future. – Thucydides, (circa 460–395 BCE)

No government, if it regards war as inevitable even if it does not want it, would be so foolish as to wait for the moment which is most convenient for the enemy – Otto von Bismarck (1815–1890)

If you will not fight when your victory will be sure and not too costly, you may come to the moment when you will have to fight with all the odds against you and only a precarious chance of survival – Winston S. Churchill (1874-1965)