Winston Churchill described World War II as “the unnecessary war” because France and Britain had authority under the Treaty of Versailles to invade Germany in 1936 when Adolf Hitler entered the Rhineland with his then-small army.
The allies failed to take advantage of this weakness at that time, and Germany rearmed.
Standing united against military aggression is the only way to prevent World War III. Russia must be defeated in Ukraine to keep it from invading the rest of Europe.