Famous economist Thomas Sowell explains.

He writes:

Despite Churchill’s legendary status today, he was not merely ignored but ridiculed at the time, when he was repeatedly warning in vain. Knowing that his warnings provoked only mocking laughter in some quarters, even among some members of his own party, he said on March 14, 1938 in the House of Commons, “Laugh but listen.”

Just two years later, with Hitler’s planes bombing London, night after night, the laughter was gone. Many at the time thought that Britain itself would soon be gone as well, like other European nations that succumbed to the Nazi blitzkrieg in weeks (like France) or days (like Holland).

How did things get to such a desperate situation, with Britain alone continuing the fight, and struggling to survive, against the massive Nazi war machine that now controlled much of the material resources on the continent of Europe?

Things got that desperate by following policies strikingly similar to the policies being followed by the Western democracies today, including some of the very same notions and catchwords being used today.

Just recently, a State Department official in the Obama administration said that Americans have remained safe in a nuclear age, not because of our own nuclear arsenal but because “we created an intricate and essential system of treaties, laws and agreements.”

If “treaties, laws and agreements” produced peace, there would never have been a Second World War. The years leading up to that monumental catastrophe were filled with international treaties and arms control agreements.

The Treaty of Versailles, which ended the First World War, imposed strong restrictions on Germany’s military forces — on paper. The Washington Naval Agreements of 1922 imposed restrictions on all the major naval powers of the world — on paper. The Kellogg-Briand pact of 1928 created an international renunciation of war — on paper.

The Munich agreement of 1938 produced a paper with Hitler’s signature on it that British Prime Minister Neville Chamberlain waved to the cheering crowds when he returned to England, and said that it meant “Peace for our time.” Less than a year later, World War II began.

Winston Churchill never bought any of this. He understood that military deterrence was what preserved peace. With England playing a leadership role in Europe, “England’s hour of weakness is Europe’s hour of danger,” he said in the House of Commons in 1931.

[…]While Russia and China increased the share of their national output that went to military spending in 2014, the United States reduced its share. Churchill deplored the “inexhaustible gullibility” of disarmament advocates in 1932. That gullibility is still not exhausted in 2015.

“Not one of the lessons of the past has been learned, not one of them has been applied, and the situation is incomparably more dangerous,” Churchill said in 1934. And every one of those words is more urgently true today, in a nuclear age.

Here’s another article by Thomas Sowell that explains it more.

Excerpt:

In France, after the First World War, the teachers’ unions launched a systematic purge of textbooks, in order to promote internationalism and pacifism.

Books that depicted the courage and self-sacrifice of soldiers who had defended France against the German invaders were called “bellicose” books to be banished from the schools.

Textbook publishers caved in to the power of the teachers’ unions, rather than lose a large market for their books. History books were sharply revised to conform to internationalism and pacifism.

The once epic story of the French soldiers’ heroic defense against the German invaders at Verdun, despite the massive casualties suffered by the French, was now transformed into a story of horrible suffering by all soldiers at Verdun— French and German alike.

In short, soldiers once depicted as national heroes were now depicted as victims— and just like victims in other nations’ armies.

[…]France, where pacifism and internationalism were strongest, became a classic example of how much it can matter.

During the First World War, France fought on against the German invaders for four long years, despite having more of its soldiers killed than all the American soldiers killed in all the wars in the history of the United States, put together.

But during the Second World War, France collapsed after just six weeks of fighting and surrendered to Nazi Germany.

At the bitter moment of defeat the head of the French teachers’ union was told, “You are partially responsible for the defeat.”

Charles de Gaulle, Francois Mauriac, and other Frenchmen blamed a lack of national will or general moral decay, for the sudden and humiliating collapse of France in 1940.

Is the same thing happening in our public schools? Are our children taught to think that wars can be prevented by unilaterally disarming?

The lesson we need to learn from history is that the way to stop wars is by making the people who want to start them understand that there will be a price to pay if they start a war. That means that we need a certain amount of military power, and that we should have demonstrated that we are willing to use it. That is counter-intuitive to people on the left who cannot imagine that evil tyrants really are evil tyrants. They want to believe that problems can be solved with talk, but history teaches that talk is cheap.