During 1938, Britain had followed a policy of appeasement – with misgivings. But when the Nazis engineered their ‘protectorate’ over Bohemia and Slovakia on 15 March 1939, Chamberlain promised to defend Poland in the event of a Nazi invasion.
The main reason for this change in policy was what Chamberlain called the ‘shock to confidence’. Chamberlain had been prepared to believe Hitler’s promise that he had no more demands for territory in Europe, but Czechoslovakia proved that Hitler had lied. The British people realised that appeasement had failed. They realised that Hitler could not trusted, and that he would only be stopped by (threat of) war.
Also, the invasion of Czechoslovakia was important because it was the first time that Hitler had taken over a non-Germanic people. Before 1939, many people in Britain had sympathised with Hitler’s aim for German unity – the Treaty of Versailles gave self-determination to every other country, why not Germany? They had hoped that German had just wanted to be secure and united. But March 1939 made it clear that Hitler’s demands for lebensraum and world domination in Mein Kampf were not just talk. The British realised that they were faced with someone who would take over the world unless he was stopped, by force if necessary.
However, the change in British policy did not happen suddenly, in March 1939. Pressure had been building up for some time for Chamberlain to change his policy. The Nazi invasion of Czechoslovakia was the trigger, rather than the whole cause, for the British change in policy.
Even in September 1938, there had been people in Britain who said appeasement was wrong. Duff Cooper, Lord of the Admiralty resigned over Munich, and in October 1938, at the Oxford by-election, three future Conservative Prime Ministers (Winston Churchill, Harold Macmillan and Edward Heath) campaigned against the Conservative candidate Quentin Hogg, saying that ‘a vote for Hogg is a vote for Hitler’. During the months after Munich, more and more people in Britain came to agree with them. Chamberlain could not have gone to war in September 1938 – too many people in Britain had wanted peace – but by March 1939, most people in Britain agreed that there would have to be a war, and he was able to promise to defend Poland.
Also, Kristallnacht in November 1939 had made people realise that, not only did the Nazi regime want world domination, but that it was an evil regime. Many Christians in Britain came to believe that God wanted them to fight against Hitler. Fascists were growing in power and people realised that they had to be stopped – in February 1939, when Franco came to power in Spain, MPs shouted ‘Heil Chamberlain’ in the House of Commons. Britain could threaten war in March 1939, because Kristallnacht had given them the moral justification to stand up to Hitler.
Finally, at Munich, Britain had not been strong enough to go to war – it is arguable that Chamberlain was just buying time for Britain to rearm. In January 1939, the navy had been strengthened and production of planes had been increased; in February, defence spending was increased to £580 million and free air-raid shelters were given to ¼ million Londoners. Chamberlain was able to change his policy in March 1939 because Britain had the military capacity to go to war.