 Complete the following phrase:  Prior to 1918, military parades followed the tradition of their larger sovereign entity, including the military tradition of Austria-Hungary. Regular military parades were held during the period of the Czechoslovak Socialist Republic, with the first parades being organized in the 1950s. The first parade of the Czechoslovak Peoples Army ČSLA took place in 1951 in Letná. Since then, parades were held every five years on 9 May to mark the end of World War II and the 