How did the invasion from Hitler in Czechoslovakia start World War 2?

Wrong country.........it was the invasion of Poland, in September 1939, that set off WW2. On September 1, 1939, Germany in pursuit of imperial control and without warning, launched a ruthless attack on Poland by land and air. Two days later, Britain and France declared war on Germany. Germany's ally was Russia, and when they defeated Poland both countries partitioned Poland.