<P> Spain negotiated with joining the Axis but remained neutral during World War II, and did business with both sides . It also sent a volunteer unit to help the Germans against the USSR . Whilst it was considered in the 1940s and 1950s to be a prelude to World War II and It prefigured the war to some extent (as it changed it into an antifascists contest after 1941), it bore no resemblance to the war that started in 1939 and had no major role in causing it . </P> <P> In 1931 Japan took advantage of China's weakness in the Warlord Era and fabricated the Mukden Incident in 1931 to set up the puppet state of Manchukuo in Manchuria, with Puyi, who had been the last emperor of China, as its emperor . In 1937 the Marco Polo Bridge Incident triggered the Second Sino - Japanese War . </P> <P> The invasion was launched by the bombing of many cities such as Shanghai, Nanjing and Guangzhou . The latest, which began on 22 and 23 September 1937, called forth widespread protests culminating in a resolution by the Far Eastern Advisory Committee of the League of Nations . The Imperial Japanese Army captured the Chinese capital city of Nanjing, and committed war crimes in the Nanjing massacre . The war tied down large numbers of Chinese soldiers, so Japan set up three different Chinese puppet states to enlist some Chinese support . </P> <P> The Anschluss was the 1938 annexation by threat of force of Austria into Germany . Historically, the Pan-Germanism idea of creating a Greater Germany to include all ethnic Germans into one nation - state was popular for Germans in both Austria and Germany . </P>

What is the reason of 2nd world war